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J. H. LOGAN, A.M.,M.D., 

Professor of General and Medical Chemistry in Atlanta 

Medical College; Author of History of Upper South 

Carolina; Member of the Academy of Science of 

Georgia ; Corresponding Member of the State 

Historical Society of Wisconsin. 

■" Omne enim Manifestatum, lumen est." — Paul. 

ATLANTA, C3-.A..: 


No. 32 Broad Street. 


£=-A.XaT FISST. 









,<3B'N this Manual, the Student will find the important 
subjects treated, so condensed and simplified as to make 
it an easy task to master them, even in the brief time 
usually allotted to such studies. He will find here, a 
differentiation, precise as possible, of Chemistry, from 
Natural Science; also, the Theory and Leading Principle 8 
•clearly and concisely defined of Heat, Light, Electricity 
and Magnetism, both as a distinctive science, and as 
related to Chemistry, Medicine, Hygiene and Practical 
Life. He will find the general Theory of Weights 
and Measures, the English System with the Art and 
Forms of Prescribing according to its standard, the 
Metrical System and the Art and Methods of Prescrib- 
ing and Dispensing by that standard, both so explained 
and presented as to be comprehended at once by any 
one who really desires their acquisition. 

Lastly, he will find a practical view of the deeply 
interesing subject of Meteorology in its present advanced 
development, and rapidly progressing claims upon th e 
Scientist, the Sanitarian and Physician. 

The author acknowledges his indebtedness to the ex- 
cellent works of Pownes, Youmans, Roscoe, Barker, Rock- 
well, Mann, the American Metrical Bureau, the State Board 
of Health of Michigan, and especially to the courtesy of 
Hall & Benjamin, manufacturers of Scientific supplies, 
.New York. 

Atlanta, Ga., January 1st, 1880. 


Physics, Chemistry and Natural History. 

AVhat is Science ? 

Science is digested, classified knowledge of 
the properties, structure and elementary prin- 
ciples of things. 
How May Science be Conveniently Divided ? 

Into three great departments, viz : Physics, 
Chemistry and Natural History. 
What is Natural History ? 

It is that branch of knowledge which con- 
siders only the form and internal structure of 
What is Physics? 

It is that branch of knowledge which treats 
of the properties of matter, whether in mass or 
molecular division. It is, therefore, properly 
divided into molar and molecular physics; the 
first embracing Mechanics, Hydrostatics, Hy- 
draulics, and Pneumatics; and the second, Heat, 
Light and Electricity. 
What is Chemistry ? 

Chemistry, since it too treats of the proper- 
ties of matter, may in that sense, be allied to 
the Physical Sciences. It considers the proper- 
ties of the ultimate division of matter — the 
atom, and lies between Physics proper and 
Biology, reposing upon the first and support- 
ing the latter. 


What is Biology ? 

In its comprehensive sense, Biology is vegeta- 
ble and animal Physiology. 
What is Matter? 

It is anything visible or tangible; anything 
which occupies space. 
How is Matter Divided? 

Into three forms— Solid, Liquid and /Eriform. 

What three Disvisions does Physics make in the Study of 
Matter ? 

It treats — 

First— Of the divisions of which matter is 

Second — Of the attractions of its particles. 

Third — Of the motions of which its particles 
are believed to be capable. 
What are these Divisions of Matter ? 

There are three— Masses, Molecules and Atoms. 
What is Mass Matter ? 

A mass is anything which can be appreciated 
by the senses. 
What is a Molecule ? 

It is the smallest part into which a body can 
be divided without loss of idenity. 
What is an Atom ? 

It is a particle more minute than the Mole- 
cule ; it is the smallest portion of matter which 
can enter into chemical combination. 
What makes up the Molecule ? 

A collection of atoms. 
What are the Attractions of Matter ,; 

There are three forms of attraction — 

First — Gravitation, or the attraction of massea 

.Second — Cohesion, or the attraction of mole- 

Vllfc.MU:0-PMYKH'S. 9 

cules. If the molecules be unlike, it is called 
Adhesive attraction. 

Third — Chemical Attraction, or the attraction 
of atoms. 
What are the Motions of Matter ? 

There are three forms- 
First — The Motion of Mass, or Mechanical 

Second — Molecular Motion, or the motion of 
the molecules in the mass. This motion in its 
variety of forms or conditions, constitutes the 
physical forces, Heat, Light, Electricity, and 
doubtless what is called vital force. 

Third — Atomic Motion, or the motion of the 
atoms, if there be such a motion. 
Do Molecules Differ ? 

Molecules must differ from each other, because 
they are composed of different atoms. These 
atoms may differ in kind, in number or in 
their relative position in the molecule. This 
is illustrated by a molecule of salt, and one of 
water, compared in regard to kind of atoms; 
and a molecule of calomel and corrosive sub- 
limate as regards the number of their atoms; 
and a molecule of starch compared with one 
of gum in respect to the arrangement of their 
What is Chemistry'' 

Chemistry is that branch of Physical Science 
which treats of the atomic composition of 
bodies, and of those changes in matter which 
result from an alteration in the kind, the num- 
ber or the relative position of the atoms 
which compose the molecule.* 
What are Physical Properties of Matter? 



They are the properties which matter pos- 
sesses in virtue of its molecular constitution. 
What are the Chemical Properties of Matter? 

They are the properties which matter pos- 
seses in virtue of its atomic composition. 
Physical Phenomena take place outside the 
molecule; Chemical Phenomena inside the 
molecule among the atoms. 
How many kinds of Molecules are there ? 

There are two; the Elemental Molecule, 
whose atoms are all alike, and the compound 
molecule, whose atoms are unlike. 
Does not this fact divide all matter into two great classes? 

It divides all matter into elemental bodies 
and compound bodies. 
What is an Element? 

It is a substance which can not be decom- 
posed into simpler substances by any known 
process — it is uncompounded. 
What is a Compound Substance ? 

It is a body made up by the union of two or 
more unlike elements. 
How many Elements are known? 

The number of the elements is sixty-four. 
Are all the Elements equally important ? 

Many of them are rare and mere curiosities ; 
only thirty-four are essential to the Student of 
Name these thirty-four Elements ? 

They are Hydrogen, Oxygen, Nitrogen, Chlo- 
rine, Sulphur, Selenium, Phosphorus, Carbon, 
Boron, Aluminum, Manganese, Iodine, Fluorine, 
Bromine, Barium, Lead, Iron, Silver, Tin, 
Zinc, Cobalt, Arsenic, Magnesium, Platinum, 
Nickel, Copper, Chromium, Strontium, Calcium, 



Potassium, Sodium, Bismuth, Mercury and 


What are the Molecular or Physical Forces ? 

They are Heat, Light, Electricity and Magne- 


Under what Heads may Heat be considered ? 
First — The Expansive Force of heat. 
Second — The Conduction of heat. 
Third — The Sources of heat. 
Fourth— Change of Molecular condition or 
State by heat. 

Fifth — Specific Heat. 

Sixth— The New or Dynamical Theory of 
What is the first effect of Heat upon all substances ? 

It expands them ; solids 
least and gases most of the 
three states of matter. 
Are not the Forms of all bodies 
fixed by Heat ? 

All bodies are eith er solid,, 
liquid or gaseous, because 
of heat. 
What then are the three most 

obvious Effects of Heat ? 
»They are Expansion, Liqui- 
' faction and Vaporization. 

Fig. 2.— Erlenmeyer's New 
Form Burner. 



What b i<lics will Heat most expand? 

It will expand most 
those bodies, whose 
molecules are least con- 
trolled by the attraction 
of cohesion; that is all 

Is this Force of Expansion 
very great? 

It is one of the irre- 
sistible forces of nature. 

Does Water Expand and 
Contract uniformly by Heat 
or its abstraction ? 
As its temperature 
approachesO°C from 4°C 
Fig. 3.-BaU and Ring. or 39 F., it gradually 
expands; though it uniformly contracted down 
to 4~l', which is the paint of the maximum 
density of water. From 0°C to 100°C water 
expands •>'•> of its volume; alcohol i; and mer- 
cury A ; water freezes at 0°C or 32°F. 
Explain Figure 3. 

The ball while cold passes easily through 
the ring, but expanded by heat it rents on 
the ring. 

How does Expansion become the measure of Temperature? 
Expansion is the effect of heat, therefore, the 
measurement of expansion will be the measure 
of the force of its cause. 
What is the usual instrument for this purpose called'.' 

It is called Thermometer or heat measurer. 
The expanding substance is a liquid and com- 
monly mercury. 
What two Thermometers are chiefly in use? 

Fahrenheit's and the Centigrade. The first 


is generally used in England and America ; the 
latter in France and by all scientists. The scale 
of F. is divided into i80 parts ; that of C into- 
100 — that is, the space between the freezing and. 
boiling points of water. Therefore, the F "scale 
is to the C as 180 is to 100, that is as 9 is to 5. 

What is the Rule for changing F readings into those of C's ?.' 
If the reading to be changed is F, subtract 
from it 32, multiply the remainder by 5, and 
divide the product by 9. If the reading be C\. 
first multiply by 9, and divide the product by 5^ 
adding 32 to the quotient. If either reading be 
negative or from below zero of the scale, it is 
only necessary to apply the algebraic rules for 
such quantities, that is, that minus multiplied 
by plus gives minus, and a larger plus quantity 
subtracted from a less negative, gives a plus or 
positive remainder and vice versa. Example— 
20°Cxl-!-32=6S° F. 

What are the limits of range of the Mercurial Thermometer?? 
It can not indicate temperature as low as- 
40°C, nor higher than about 350°C, because mer- 
cury freezes at the first point and boils at the 

What fluid is used instead of mercury for lower tempera- 
tures than— 40° C, and what Instrument for higher tem- 
peratures than 350° C ? 

Colored alcohol is used for the lower tempera- 
tures, because no known degree of cold com- 
pletely freezes it. An instrument called the 
Pyrometer, fire measurer, is in use for the- 
What is the Clinical Thermometer ? 

It is an instrument, more frequently used by 
physicians, to ascertain the temperature of the 
body in disease,the normal temperature being 98° 


or 99° Fahrenheit. Itshould be self-registering. 
How is this instrument applied ? 

Alter the patient has rested about nn hour in 
bed. the bulb of the thermometer is placed deep 
within the axilla, the arm of the patient being 
folded across the breast. The instrument should 
remain in this situation five or ten minutes, and 
the indication must be noted before it is re- 
moved, if it be not self-registering. 
Are the teachings of the Clinical Thermometer important' 

This instrument has been but a short time in 
use by the medical profession, and has already 
established certain laws of temperatnre in dis- 
ease, which are of great value. 
What are the most important of these Laws? 

First — That in fevers and other acute diseases, 
the temperature of the body is uiised above the 
normal standard. 

Second — That if the thermometer in the ax- 
illa does not indicate a temperature above 98° 
or 99° F., there is no fever present. 

Third — That the range of increase of heat in 
different febrile diseases extends to 110° F., the 
amount of increase being a criterion of the in- 
tensity of the disease. The increase to 100° or 
101° is evidence of a mild invasion. If the 
thermometer indicate persistently 105° it is cer- 
tain that the attack is severe. A temperature 
of one or more degrees above 105° indicates 
great danger, and if it rise to 109 a or 110° F., 
death is sure to follow. 

Fourth — That whatever may be the other 
symptoms of a disease, its force is not abated, 
so long as the thermometer indicates increase 
of temperature. 

Fifth — That a progressive increase of heat, 



from day to day, denotes a corresponding in- 
crease in the severity of the disease, while a 
gradual reduction of heat to the normal standard, 
defervescence it is called, indicates convales- 

Sixth — That in some diseases, especially 
Typhoid fever, there is oscillation of tempera- 
ture between night and morning, the maximum 
at night and the minimum in the morning, so 
that the thermometer most be used at least 
twice a day.* 
What is Bunsen's Burner ? 

It is a simple contrivance by which atmos- 
pheric air is burned with gas. thus producing 
an intensity of heat, which the gas alone is 
incapable of doing. 
Describe Bunsen's Burner. 

It is a metalic tube, resting at its lowest ex- 
tremity upon a box, whose sides and bottom are 
pierced with several holes by which gas and air 
are admitted before reaching the flame above. 
The air may be admitted or shut out at pleasure. 
The instrument may be constructed so as to 
consist of two or more tubes combined, thus 
multiplying its power. 

What instrument is represented in 
Figure 18 ? 

This is Bunsen's Blast Lamp 
or Burner. It is adjusted so as 
to have universal motion, and 
is an instrument of great power. 
The principle of its action is 
readily understood. 

*See Flint's Practice of Medicine, page 107. 


What is Li qui faction ? 

It is the conversion of a eo'.id into a liquid by 
the agency of heat. 
What is Vaporization ? 

It is the conversion of a liquid into a vapor 
by the agency of heat. 
What h Evaporation? 

Evaporation is slow vaporization, general and 
spontaneous, at ordinary temperatures. 
What is Condensation ? 

It is the abstraction of so much heat from a 
vapor, as to restore it to the state of a liquid. 
What is Ebullition? 

It is violent vaporization, produced by the 
rapid formation and rising of steam bubbles from 
the bottom of a heated vessel. 
What is the Boiling Point ? 

It is the point at which any liquid begins to 
vaporize rapidly or violently. Liquids differ in 
this respect; so that a liquid's boiling point is 
one of its important characteristics. 



What is Distillation? 

The distillation of a liquid, is vaporizing it 
in one vessel by heat, and condensing it by cold 
in another. In this way liquids are often sepa- 
rated from each other, as well as purified. See 
fig. 4. 
What is the Fusion or Melting Point of Solids ? 

It is the point at which any solid body 
passes, by the agency of heat into a fluid. The 
melting point of solids, is also one of their im- 

18 student's manual of 

portant characteristics. In the case of a single 
metal, iron, another very important property 
is that it softens before fusing. 
What is Sensible Heat ? 

It is the heat that may be indicated by the 
What is Latent Heat? 

It is the heat which disappears, or is lost by 
any solid or liquid, in passing the one into a 
fluid and the other into a vapor. This is called 
the heat of fluidity. Any fluid contains more 
heat than any solid, and any vapor more than 
any liquid. 

What is the Cryophorus ? 

It is an instrument designed to illustrate the 
cooling power of the process of evaporation. 
The name is derived from the Greek — kruos, 
ice and phero, I bear. 
Describe the Cryophorus. 

It consists of a tube, having a bulb of glass 
at each extremity. The air is first expelled 
from the instrument by boiling a little water 
contained in one of the bulbs, and sealing the 
opening through which it escaped, while the 
tube is full of vapor. If the empty bulb be 
noV placed in a freezing mixture, the vapor 
condenses and produces so rapid an evaporation 
from the water that it instantly freezes. (See 
fig- 5.) 
This Latent Heat lies hid, but is it lost ? 

No; it is insensible, because it has been con- 
verted into something else — into an equivalent 
of mechanical work. It is this work or force 
that maintains the substance in its fluid or 


gaseous state; a condition of potential energy. 

May this Mechanical force among the molecules be re-con- 
verted into Heat, thus restoring' it all again? 

When any liquid becomes a solid again, or 
any vapor a liquid, the exact numerical equiva- 
lent of the heat, which had been converted, is 
restored and may be indicated by the thermom- 
What simple experiment proves this loss or conversion of 


lib of water at 32°F. j ■> ..' . wntOT , mt 1(V o ,o 
„. oal? y =1 ,bs. ot water at 10.11 , 
1 lb. of water at 1 / 4.2 Y . j 

1 lb. of water at 1742°F. ) =2 lbs. of water at 32°, 
1 lb. of ice at 32°F. j but the ice is melted. 

The first mixture gives a mere mean of the 
two; the second, shows a loss of 142,2° which 
were consumed in melting the ice. 

In the first mixture, the result is only the 
mean of the two temperatures. In the second, 
it is a loss of 142 2°, obviously consumed in 
melting a weight of ice equal to that of the 
water; a quantity which would raise one 
pound of water through a range of 142 2o F. 

The sudden increase in volume, exhibited by 
water in the act of freezing, whose fo.ce is so 
enormous, has no relation, whatever, to the 
gradual expansion of pure water below 4° C. to 
0° C. 
What aie the Laws relating to the Expansion of Gases? 

First — All gases and vapors expand nearly 
alike for equal increments of heat. 

Seco d — The rate of expansion is not altered 
by an increase or diminution of pressure. 

Third — The rate of expansion is uniform for 
all degrees of heat. 



Fourth — The constant increment of expan- 
sion for every degree above 0° C. is expressed 
by the fraction vH- of its volume, or which is 
more convenient for calculations, - 3 -Hir- 
What is Mariotte's Law ? 

The volume of any gas is inversely, and its 
density directly as the pressure to which it is 
What is meant by the Density of a Gas ? 

It is the weight of a given volume of gas, as 
compared to an-equal volume of hydrogen. Its 
specific gravity would be the same volume 
compared to an equal volume of air. 
How may the Specific Gravity of any gas be obtained ? 

The specific gravity of hydrogen is 0693; 
this number multiplied upon the density of any 
gas must give its specific gravity. Hence it 
follows, that density may be obtained by di- 
viding specific gravity by 0.0693. 
Whet is a Heat-Unit ? 

The heat of combustion is measured by heat- 
units; a heat-unit being the quantity of heat 
required to raise 15.43 grains, or one gram of 
water from 0° C. to 1° C. Since one gram or 
15.43 grains of carbon, burning in oxygen, gives 
8080 units of heat, it would raise as many grams 
of water through the same number of degrees. 
Knowing the amount of carbon in any given 
fuel, it is easy to calculate its heat-giving value. 
What is Joule's Law expressing the Mechanical Equivalent 
of Heat? 

The quantity of heat required to raise one 
pound of water 1° F. will evolve a force adequate 
to raise a mass of 772 pounds one foot high, or 
of one pound 772 feethigh. 


These, by way of distinction, are called "foot 


This law, therefore, is based upon the effect 


What is the Elastic Force of a Gas ? 

The force with which a vapor or gas expands 
is called its elastic force or tension. One cubic 
inch of water will expand by heat into nearly 
one cubic foot of vapor or steam. 
What is Specifiic Heat? 

All substances have not the same readiness to 
be raised by heat through 1° F. or any other 
range of the thermometric scale; they all differ 
in this respect, each one having its own capacity 
for heat; this is its specific heat, and the 
measure of it is the quantity of heat, compared 
with that of water required to raise it through 
1° F. that is one heat-unit. 
What is the highest Specific Heat known ? 

That of hydrogen gas is the highest known 
to science. Water possesses the next highest 
capacity, and is the unit of measure for all spe- 
cific heat. Water being 1, the specific heat of 
hydrogen is 3.409, and air being 1, the specific 
heat of hydrogen is 14.451. The specific heat 
of all other substances, is of course, expressed 
In how many wars is Heat communicated? 

In three — by conduction, when it passes from 
particle to particle of the heating body ; by 
convection, as when heat is conveyed by parti- 
cles moving from one part of the heating sub- 
sance to another; by radiation as when heat 
darts, as it were, through some portion of space 
from a hot body to a cold one. 

22 student's manual of 

What bodies are the best conductors ? 

Dense, solid bodies such as the metals. 
Are liquids good conductors ? 

They are jilmost non-conductors. 
Are Gases and Vapors good conductors ? 

iEriform bodies are yet worse conductors than 
liquids, air being about the worst conductor of 
them all. All fluids, embracing under that term 
both liquids and aeriform bodies, are heated 
chiefly by convection. 
How does Radiant Heat move ? 

It moves in straight lines from object to object, 
and is by these either reflected, absorbed, or 
transmitted. The law of its reflection, is that 
the angle of reflection is always equal to that 
of incidence Good absorbers are poor reflectors, 
and vice versa. Heat in passing through most 
substances, is more or less intercepted or re- 
tained The heat of the sun, however, passes 
through transparent substances without loss; 
but heat from the earth is in great part arrested, 
especially by such substances as water, alum and 
glass. This fact is very important. 
What are the Sources of Heat ? 

They are five; the sun, the interior of the 
earth, Electricity, mechanical action and chem- 
ical action. Tbe greatest of these is the sun. 
How is Chemical Action a Source of heat ? 

When substances have their original consti- 
tutions broken up or altered, by being combined 
chemically with other substances, more or less 
heat is evolved; this is the heat of chemical 
action; it is also the same as that called the 
heat of vital action. 
What is the Heat of Mechanical Action ? 



Heat and mass motion are always convertible 
one into the other, as by the friction of two 
solid or liquid bodies. This is the heat of me- 
chanical action. 

What is the Theory of Heat existing in the Interior of the 
Earth ? 

There are good reasons for believing that the 
interior of the earth from a depth of some fifty 
miles from its surface to the centre, is in a state 
of fusion. 

How is Electricity the Source of Heat ? 

Electricity, like heat, is convertible alike into 
mechanical motion, chemical action and heat. 

What is Heat ? 

It is now defined according to the dynamical 
theory, to be a mode of motion of the molecules. 
Intensity of this motion is the measure of tem- 
perature. Of the nature of heat nothing is 

What is Dew ? 

It is the moisture of the air con- 
densed upon bodies, with which it is 
in contact, colder than itself. It is a 
product of radiation. 
What is meant by the Dew Point ? 

The temperature of the air at which 
condensation of its moisture takes place, 
is the dew point. This point is con- 
stantly varying. Frost is frozen dew. 
Clouds are partially condensed vapor- 
in the higher regions of the_ atmos- 
phere. Fog and mist are condensed 
vapor at the earth's surface. Evapora- 
Fig.5. tj on takes nlace from the surface of 

24 studekt's manual of 

bodies only, and depends, in great degree, upon 
the stillness, dryness, temperature and density 
of the atmosphere. 
"What is the Tension of a Vapor? 

It is the force, expressed in inches of the 
barometer,* with which a vapor according to 
temperature, resists atmospheric pressure. The 
tention of w'ater at 0°C, or 32°F. is 0.20 inches 
of the barometer; at 82°C or 1S0°F. it is 15.15 
inches, and at 100°C. or 212°F. it is 30.00 inches 
of the barometer. 
Does Air absorb moisture at all temperatures? 

It does, and retains it in an invisible state. 
The higher the temperature the greater this 
power. Air is said to be saturated with mois- 
ture, when it coi tains as much as it can hold 
with a given temperature. The air usully con- 
tains from fifty to seventy per cent, of the satu- 
rating quantity of moisture. If the quantity 
be not within these limits, the air is disagreea- 
bly dry or moist. 
How is the quantity of Moisture in the Air with any tern 

perature ascertained ? 

By an instrument called the Hygrometer. 
Paniell's is the best in use. 
What is the action of this Hygrometer ? 

The condensation is produced by the evapor- 
ation of ether. It is thus, constructed : A glass 
tube being bent twice at right angles, having a 
long and short arm, each terminating in a bulb, 
the bulb of the short arm is wrapped in a piece 
of muslin, and that of the long arm half-filled 
with ether, into which a delicate thermometer 
dips. On the stand of the instrument is adjus- 

This instrument will be desci Ibed In another place. 


ted another thermometer to show the tempera- 
ture of the air. 

How is an observation marie with it? 

First pour a little ether upon the muslin 
wrapper; its evaporation quickly lowers the 
temperature of the other hulb, and when it 
reaches the dew point, a film of moisture is seen 
upon its surface. The thermometer in the tube 
indicates the temperature of this deposition, 
and fixes the dew point. But this observation 
merely shows the dew point to be high or low. 

Can m it the observation lie extended so as to ascertain the 
absolute amount of moisture in a given volume of air? 

It can, and its importance to the student re- 
quires a particular explanation of principles 
and practical details 

We know that the vapor of water or steam, 
at 212° F. under a pressure of 30 inches of the 
barometer, is 1,700 times lighter than an equal 
volume of water at its maximum density of 40° 
F. Now a cubic foot of water, at that tempera- 
ture weighs 437,272 grains; therefore, the 
weight of a cu. foot of steam, at the same tem- 
perature and pressure, is 437,272-4 - 1,700=257.- 
218 grains. Hence under Boyle's law,— density 
is directly as the pressure — it is easy to calcu- 
late the weight of the same volume of steam of 
the same temperature under any other given 

Suppose the reading of the dew-point thermometer is 50° F. 
it is desired to know what is the amount of moisture in a 
cubic foot of air at this temperature ? 

Obviously the elasticity of the watery vapor, 
present, corresponds to a maximum density in- 
dicated by 50°, and according to a table of great 

26 student's manual of 

value, prepared by Dalton, it supports a barom- 
etric column of 0.400 inches. It follows, that 
30: .400::257.218=3.426 grains of watery vapor at 
212° and 30 in. weighs 257.218 grains, an equal 
volume of vapor, of the same temperature, sup- 
porting a column of 0.400 in. will weigh 3.426 

But now what will it weigh at the given temperature of .50° ? 
This brings us to the rule of reducing gase- 
ous volumes for temperatue, according to Gay 
Lussac's Law : "All gases expand or contract, by 
the same amount for the same increase or 
dimunition of temperature." The amount of this 
increase or contraction is -tio of its volume for 
every degree of Fahrenheits thermometer from 
32°. Hence, taking a volume of gas at 32° as 
unity, its volume at 50° is to its volume at 212° 

CIO ± — | 4t>U . i. | 4bU. 

The denominator, 18 is derived from 50° — 32° 
and 180 from 212-32 The expression 1-|-«'A 
simplified is, 1, 0391, and l-|-lfu,is 1,375. Hence 
50:212::1,0391:1,375, or 1,0391:1,375::3.426=4.534 
grains, since it was just seen that a volume of 
air at 212" and 0.400 inches tension would weigh 
3.426 grains. 

How is all this calculation simplified, and made practically 
easy ? 

The above is a demonstration of the princi- 
ple of these observations; but Dalton's table of 
gaseous tension for temperature with the cor- 
responding results in grains per cubic foot of 
vapor, saves the trouble of repeated calculations, 
It should be copied by the pupil, and pasted up 
for convenient reference : 




Elastic Tension. 

Weight of Cubic Foot. 


.068 inches. 

8.856 grains. 


.083 " 



.098 " 



.119 " 



•140 " 

1 688 


.17o " 



.200 " 



.240 " 



.280 " 



.340 " 



.400 " 



.476 " 



.560 " 



.657 " 

7 230 


.770 " 



.906 " 



1.060 " 



1.235 " 

13 081 


1 430 " 

15 005 


1.636 " 





Does the above Method apply to all Hygrometers ? 

It is only applicable to the condensation 
How many classes of Hgrometers are in uee ? 

There are two, the Condensation Hygrometer 
and the Absorption Hygrometer. The former 
is the only one that is reliable. 
Suppose a reading of the dew-point thermometer fall 

between any two of the numbers in the first column of the 

table ? 

Iii that case take the number in the second 
column, nearest to the reading, either above or 
below; the error will be inappreciable. For 
greater accuracy, see section on Meteorology. 



Absolute Weight, Specific Weight, Atomic Weight, 
Molecular Weight, Molecular Volume. 

What Weights are used in Chemistry and Physics? 

They are four in number, absolute, specific, 
atomic and molecular weights. 
What is Absolute Weight ? 

It is the weight of the whole mass of a bod}' 
without reference to its volume. 
What i< Specific Weight or Gravity 1 

It is the weight of a given volume of any 
substance compared with the weight of an equal 
volume"of some other substance. 
What is Atomic weight ? 

It has already been noticed that atoms differ 
from each other in quality, quantity and weight. 
Atomic weight is the relative weight of any 
atom referred to hydrogen as unity. It is the 
smallest quantity of any substance by weight, 
which can enter into combination. 
What is Molcular weight ? 

It is the weight of a simple or compound Mol- 
ecule, and is formed by taking the sum of the 
atomic weights of its constituent atoms. 
How is absolute weight ascertained ? 

By the methods of two systems, known as the 
English and French, or Metrical system of 
weights and measures. 

Why is it important- that the student should acquaint him- 
self with the Metrical system? 

Because it is already universally adopted by 
scientists, and promises to become soon the le- 
galized system of all civilized countries. 

How is Absolute weight ascertained in Chemistry ? 

By means of the chemical balance, an instru- 
ment of marvelous accuracy, beauty, and useful- 
ness. Loaded with ICO grams, or 1,543 grains, 
it will still indicate the one-millionth part of 
the substance weighed. 

Hew is the specific weight or gravity of solids and liquids 

As specific gr. is relative weight, it is con- 
venient to have some fixed standard ; for solids 
and liquids, this standard is pure water at the 
temperature of 60° F, since the volume of 
bodies varies with temperature and consequent- 
ly their density. 
What is the practical rule for obtaining it? 

Divide the absolute weight of a given volume 
of the substance, by the weight of an equal bulk 
of water. 
How is the Spe. Gr. of a solid lighter than water obtained ? 

Divide the weight of the solid by the sum of 
its weight added to the loss of weight, which it 
occasions in a heavy body previously weighed 
in water. Example : A body lighter than 
water caused the loss of 10 lbs. to a heavier body 
immersed in water. In air the same body 
weighed 30 lbs., what was its Spe. Gr. ? 30-|-10 
=40, then 30-! — 40=. 75, the answer 40 is equal 
to its own volume of water. 
How is the Spe. Gr. of a body heavier than water obtained ? 

Weigh it in the water and out of the water 
and divide as before the weight out of the water 
by the loss of weight in the water. 
-How is the Specific Gravity of a Liquid obtained? 

The most reliable method is by means of the 
specific gravity bottle. Balance on the scales d 
bottle holding 1,000 grs of water at 60° F.; now 



remove the water, and after filling the bottle 
with the liquid in question, weigh again; divide 
this last weight by the first and the result will 
be the specific gravity. Mark the h eighth of 
the water in the neck of the bottle with a file, 
and it need not be balanced except for the liquid 
in question. 

What is the usual, but less accurate, method of ascertaining 
Specific Gravity of Liquids? 
By means of the Hydrometer. 
What is the Hydrometer? 

It is an instrument for ascertaining the Spe- 
cific gravity of Liquids. 
What is the principle of the Hydrometer? 

It is, that the greater the density or weight 
of a liquid, the greater will be its buoyancy. 
How is the Hydrometer constructed ? 

There are various hydrometers, but it usually 
consists of a hollow ball of g'ass, having a grad- 
uated stem. A weight is also attached to the 
ball beneath to steady it in the liquid. 
What is a special Hydrometer? 

It is one, which is adjusted 
exclusively to some particular 
liquid. There are several of 
these instruments, such as 
the alcoholometer, lactometer, 
urinometer, etc. Some are 
known by the names of their 
inventors, as Beaume's & 
Nicholson's hydrometers. 

Nicholson's Hyilromctc r. 


What is Nicholson's Hydrometer? 

It is a hollow cylinder of glass or metal, Fig. 
4, weighted at the bottom, and having a small 
basket suspended at the same point. Above is 
a stem supporting a plate, on which small 
bodies and weights may be laid. 
How is this Instrument n-ed ? 

We first ascertain by it the absolute weight 
of the object; then the weight of an equal 
volume of water, and apply tbe given rule for 
obtaining spe. gr. 
What is the Process? 

The instrument stands vertically in the water; 
lay the object on the plate, and add weights till 
the instrument sinks to a marked point on its 
body or stem. Remove the object, and add 
again, as much weight as will sink the instru- 
ment to the same point. This will be its abso- 
lute weight. 

Now put the object in the basket below, after 
removing the weight above. The instrument 
buoyed by the object in the water, will not sink 
to its fixed point. Add weight to sink it that 
far, and this will be the weight of an equal 
volume of water. Then apply the rule. 
How is the Specific Gravity of Gases obtained? 
. Air is taken as the standard specific gravity 
for gases and vapors, at the temperature of 32° 
F., and the barometric pressure of 30 in. for the 
density of gases, it will be seen, varies both 
with temperature and atmospheric pressure. 
What is the Process? 

The same rule applies as for solids and liquids. 
Weigh the gas, and divide this number by the 
weight of an equal volume of pure air. A glass 



flask is first weighed, absolutely empty, it is 
then weighed full of air, this gives the standard 
measure. The gas is now I alanced in the same 
flask, and the number divided by the weight of 
the air. 

What relation does the Metrical System bear to the subject 
of Specific Gravity ? 

Ail the practical applications of its theoiy are 
simplified to the utmost degree by the methods 
of the metrical system of weights and measures. 
It does this, not only for solids and liquids, but 
for vapors and gases as well; and for all alike, in 
the domains of chemistry, physics, manufacture, 
art and trade. 

How is the Specific Gravity of a Liquid determined by the 

For liquids heavier than water, the scale in- 
creases from the water, zero, downwards; for 
liquids lighter than water, it increases from zero 
upwards. The urinometer is graduated to hun- 
dredths of the unit; it is only necessary, there- 
fore to add i's indication to 1,000, to obtain the 
specific gravity. 
What is the difference between the Density of a Gas and its 

Spe. Gr. ? 

These terms are sometimes used interchange- 
ably ; it is proper, however, as has been done in 
Chemistry, to use the word density to indicate 
weight of a given volume of gas, as compared 
with hydrogen, and the term Spe. Gr. to indi- 
cate, in like manner, the weight of a given vol- 
ume of gas referred to air as a standard. The 
density of oxygen, for example, is 16; its Spe. 
Gr. is 1. 1087; the density of hydrogen is 1 ; its 
Spe. Gr. is 0.0693. Density implies a unit of 
volume ; Spe. Gr. is mere ratio. 


Why is it important to ascertain Spe. Gr. ? 

Spe. Gr. is one of the most important of the 
physical properties of matter. It is often the 
means of identifying useful substances without 
further investigation, and quickly reveals the 
presence of adulteration in articles of food, med- 
icines, and materials of manufacture and art. 


The Atmosphere, The Barometer, The Air-Pump, 
Pneumatic Cistern, Diffusion of Gases. 

What is Pneumatics ? 

It is that branch of Physics which treats of 
the motion, and pressure of gases and vapors. 
AVhat is the Atmosphere '? 

It is the gaseous substance which surrounds 
the earth, like an ocean, having a depth of more 
than fifty miles, and which gives life to all or- 
ganic forms on its surface. 
Has the Atmosphere weight? 

All gases and vapors, being matter, necessa- 
rily possess weight. 
What is the most remarkable property of Gases ? 

All gases and vapors are in the highest degree 
elastic. The space which a gas occupies de- 
pends upon the amount of pressure exerted 
upon it. There is no known limit to their 
expansibility as pressure is removed. 
What is Boyle's Law ? 

The volume of a gas is inversly as the pres- 



The density and elastic force are. directly a? 
the pressure. 

The density of a gas is inversely as the 
What is the Law of Charles ? 

Any volume of gas, under a constant pressure, 
varies directly as the absolute temperature. 
What is Avogadro's Law? 

In the condition of a perfect gas, all substances 
under like conditions of temperature and pres- 
sure, contain, in equal volumes, the same num- 
ber of molecules. 
What importance has this law? 

It is the basis of the modern system of chem- 
istry. In the field of the New Chemistry, its 
discovery is like that of the attraction of gravity 
to physics, by Sir Isaac Newton. 
What is meant by the Reduction of Gases ? 

It is sometimes necessary to reduce gaseous 
volumes, both for pressure and temperature 
under the normal pressure of thirty inches or 
760 milimeters. 
What is the simple rule of this reduction for Pressure ? 

Multiply the given volume of gas by the 
barometric height under which it was measured, 
and divide the product by 30 or 760 m. m.; the 
-quotient is the true volume. 
Example — What is the true volume, which 15 cubic inches 

of hydrogen measured at 2!) inches would have, if meas- 
ured at 30 inches ? 

By the formula — 15x29—30=14.5 cubic inches 
What is the Reason of this Rule ? 

Let H equal the given barometric height. 

H' equal any other barometric height. 

V equal volume corresponding to first barom- 
etric height. 


V equal volume corresponding to second 
barometric height ; then by Boyle's law, since 
volume is inversely as the pressure, we have the 
proportion— V: V':: H': H. Hence V H'=V H 
or V'= -gr. This equation is the formula from 
which the verbal rule has been constructed. 
"What is the Rule for the reduction of gases for temperature ? 

By the law of Charles, all gasses, expand or 
contract by the same amount, for the same in- 
crease or decrease of temperature. The amount 
of this expansion — its coeficient — is ihu of the 
gas at 32° for every degree F. or ria, if by con- 
tigrade, at QP.xb=. 002174; ih= 003665. The 
rule, therefore, may be thus stated ; for increas- 
ing volume, multiply the given volume by 
unity augumented by the product of .002171 or 
.003665 by the number of degrees the tempera- 
ture is raised. For a decreasing volume, divide 
the given or known volume by unity, increased 
by the product of the coeficient by the number 
of degrees the temperature is lowered. 
What is the reason of these Rules ? 

Let Y=the known volume. 

V'=the unknown volume ; and 
t Q =the number of degrees, the tempera- 
ture is raised or lowered, then V — Vx(l-f-.003- 
■665 1), for if .003665 is its expansion at Q , 1+ 
003665 will be the expansion at 1° by the law, 
and 1+.0036G5+2 at 2° and 1+003665x3 at 3 a 
and l+(003665xt) volumes at _t Q . 

So that the above equation is the formula for 
the first rule, and the second is easily deduced 
from it by transposition of terms: V= (f _, . 003(Kir , t) 
the formula of the secc nd. 


Example— A gas measures .S)15i cubic inches at 9° what 
will it measure at G0° ? 

V = .9154x(l + .003665x60) = 1.1167 cubic 

A gas measures at 100° 40.1 c. c, what will it measure 
at 0° ? 

V -^-^kluo]= 29 - 345 c - c.-answer. 
What is the amount of pressure of the Atmosphere for 
each square inch of surface at the sea level ? 
It is 14.6 lbs. or nearly 15 lbs, and this is 
called an atmosphere; 30 lbs. would be 2 atmos- 
pheres, etc. 

Was the Weight of the atmosphere known to the Ancients ? 
This fact has been known only 
since the days of Torricelli, about- 
200 years. 

Fig. 3-Magrleburg 

What is a Vacuum ? 

It is a portion of space where no matter is. 
There is no perfect vacuum. 
When the air is removed from a tube or jar in water, why 

does the water instantly till it ? 

Because the air being removed, a vucuum is- 
formed, and the pressure of the Atmosphere 
upon the surface of the liquid external to the 
tube, forces it up to occupy the place of the air, 
there being no longer any elasticity of the air 
above to resist it. 
What are the Magdeburg Hemispheres ? 


In 1654, Otto Guerike made the first exhibi- 
tion of the powers of the air pump, by a pair 
of Magdeburg Hemispheres. These consist of 
two hollow cups of brass fitting air tight, which 
being united, are screwed to the plate of the 
air pump, the air exhausted in their interior, 
and the vacuum secured by means of a stop- 
cock. The cups cannot, now, be separated 
without a great force antagonizing the pressure 
of the external air. Fig. No. 3. 
What is the Syphon ? 

It is a tube bent like the letter U, so as to 
have one leg or side longer than the other, to 
■contain a longer column of water or other fluid. 
What is the principle of its action ? 

The longer column having the greater hy- 
drostatic pressure, the fluid must run in that 
direction, while the upward pressure in the 
shorter leg will sustain the flow so long as its 
open end remains below the surface of the fluid. 
Describe the Cup of Tantalus. 

This curious toy consists of a cup or 
tumbler, with a syphon concealed within. 
The water being poured in, will, of 
course, rise in the shorter leg, which 
opens in the cup, and, as soon as it rises 
above the bend, it must begin to escape 
by the longer leg, which opens outside 
^Ip^f through the bottom. Fig. G. 


Who discovered this Principle? 

Torricilli, 1642, the famous pupil of Galileo. 
How did this discovery lead to the invention of the Ba- 
rometer ? 

Torricelli, (Torrichelli) had used a glass 


tiibe more than thirty inches in length, which 
he filled with mercury, one end being open, so 
as to compare its height with that of water in 
the common suction pump. This column of 
mercury was observed to fluctuate, from day to 
day, within a certain space, and, therefore, to 
indicate variations in the weight of the incum- 
bent atmosphere. The addition of a simple 
scale of inches or milimeters, to a mounted tube 
to mark these fluctuations gave origin to the 

is the cause of these variations in the weight of the atmos- 
phere well understood ? 

Several theories have been advanced to 
account for them, but none is wholly satis- 
What are the different forms of the Barometer? 

There are various forms of this useful instru- 
ment, but the principle is the same in all. 
Those most in use are the cistern and siphon 
barometers. The wheel barometer is a mere 
toy, and the aneroid, though elegant and inge- 
nious, is liable to get out of repair. 
What is the construction of the Cistern Barometer? 

It is merely the inverted tube of Torricelli, 
thirty-four inches in length, and rests at one 
end in a cistern of mercury, to which the air 
has free access. The siphon barometer is the 
same tube bent in the form of the siphon. It 
is inferior to the first instrument. 
On what does the value of the Barometer depend as a scien- 
tific instrument ? 

It depends on the purity of the mercury and 
the total exclusion of atmospheric air. For 
this reason, the most carefully constructed in- 
struments are liable to gradually deteriorate. 


How may a Cistern Barometer be easily tested ? 

Carefully invert the tube, and let the mer- 
cury fall with some force upon the closed ex- 
tremity. In a perfect instrument the stroke 
will give a ringing metalic sound, but if air or 
other impurities be present the sound will be 
What are the uses of the Barometer ? 

It is valuable in Astronomy to determine the 
amount of atmospheric refraction; it indicates 
climate by determining attitude; it measures 
the height of mountains and table lands; it is 
indipensible, as already seen, in certain impor- 
tant reductions of gases and vapors, and in 
connection with the vast telegraphic systems 
of the age, it has become invaluable as an indi- 
cator of approaching storms and changing 

How has the Telegraph enhanced the value of the Barometer 
as a weather indicator? 

The chief points to be attended to, in obser- 
vations by the barometer, are its fluctuations 
taken in connection with the wind and the 
state of the sky, but, above all, its readings as 


What corrections are required for nicely accurate barome- 
tric readings ? 
There are three possibly; the corrections for 

Capillarity, for Temperature and for Capacity. 

What is the Reason of the correction for Capillarity ? 
The effect of the attraction of the walls of a 

glass tube upon mercury, is what is called 

Dram, of Tulis 











reversed capillarity. That is, the metal, in- 
stead of rising like water in the bore, is con- 
siderably depressed, so that the apparent read- 
ing is not the true height of the column. It is 
too low, a fraction must be added, and this 
quantity varies inversely as the diameter of 
the tu!>e. 

If the diameter equals .6 of an inch no cor- 
rection for capillarity is required. 

The following table gives the corrections foi 
different diameters : 
Diam: of Tube Depression 
inches. ' inches. 

.10 .uo:; 

.15 .0863 

.20 .0581 

.25 .0407 

,30 .0292 

.35 .0211 

What is the Rule for correction for Temperature ? 

Subtract the .0001 part of the observed height 
of the mercury for every degree of Fahrenheit 
above o2 J . 

Example — Suppose the Thermometer — which is appended 
to every approved barometer: — indicates 60°, while the 
liarometer stands at M0 inches, the correction will be 
(00 — 32x30x.0O01=.084 This number being substracted 
from the observed height, reduces it to the corresponding 
heat at :!2°, this being the unit of heat for expansion ol 
the mercury. 
AVhat is the reason of this Rule ? 

The column of mercury in the barometer is 
affected by variations of temperature precisely 
as that in the tube of the thermometer, and 
thus the accuracy of its readings is viciated, 
more or less, for every degree of temperature 
above the freezing point of water. 

( 'orrection for temperature, therefore, consists 
in first finding, and then removing the temper- 


ature expansion of the column from its eleva- 
tions due, alone to atmospheric pressure. 

Let x=the correction sought; 

Let b=height of mercury in barometer ; 

Let a=height above freezing point of mer- 
cury in thermometer; 

32 Q =unit of heat for mercury expansion, 
.0001 being the increment of expansion for 
every degree above 32°F., then we have x=b — 
(a — 32)bx.0001, the formula for the rule. The 
increment of expansion of mercury from 32° to 
212 J by Fahrenheit's scale is rfe=.0001 nearly ; 
and by centigrade it is m'nf, also, equal nearly to 
.0001. As in the use of the hygrometer, all this 
is simplified and made easy in practice, by a 
convenient table of corrections for each degree 
of the scale from 32" to 100 a , and for every halt 
inch of the barometric scale from 27.5 to 30.5 
inches. The student can construct one for his 
own use from the formula. The following are 
corrections, for two degrees of the thermometer 
for each half inch of barometer: 
Barometer Scale. Temperature. Corrections. 

inches, i inches. 

28 I .0028 
28.5 ,(H)28.-, 
2!) 33° .0020 

29 5 .0020:. 

30 .00030 
30.5 J .00305 
28 1 .005(1 

28 5 .00570 

29 .,,0 .0058 

29 5 .00205 

30 .0000 
30.5 J .00010 
28 1 -,o .0610 
28.5 } dl .06270 
28 >- 100° .1004 



What is Correction for Capacity ? 

This is simply an adjustment by which the zero 
point of the scale it made to correspond with 
the level of the mercury in the cistern. This 
is done either by causing the scale to move 
towards the cistern or ',he cistern to the scale. 
The latter is the usual adjustment in good in- 
What is the Reason of this Correction ? 

As the mercury rises or falls in the tube, there 
is, of course, less or more of the fluid in the 
cistern. Its surface level no longer corresponds 
with the zero of the scale, and consequently the 
readings of the instrument do not give its true 
indications. This correction is provided for by 
means of adjusting screws in all perfect cistern 
What is the Pneumatic Trough or Cistern ? 

It is a vessel of glass or metal, usually de- 
signed to collect and preserve gases. Having 
the form of a tank, it is filled with water or 
mercury, and supplied with perforated shelves 
on which glass jars, inverted and filled with 
water or mercury, stand ready to receive the 
gases, delivered through the perforations over 
which they rest. See Fig. 19. 



Fig. 19— Pneumatic Cistern. 
What causes the fluid to be supported above its level in the 

jars after their inversion ? 

Because, as already explained, the pressure of 
the atmosphere on the surface of the water or 
mercury in the cistern sustains the column of it 
in the jar. 
Why do gases pass from a delivery tube into the jar. thus 

inverted, aDd gradually displace all the liquid suspended 

in it ? 

Gases are lighter than water, and must, when 
free to move in it, rise to the surface. But gas 
and water can not occupy the same space at the 
same time, on the principle of the irrisistibility 
of matter; that is, no two bodies can occupy the 
same portion of space at the same moment. 
Therefore, the liquid flows out and gives its 
place to the gas. 
What is the Air Pump ? 

It is a machine for exhausting the air from 
any vessel suited to the purpose. See Fig. 1. 

What is the Principle of its construction ? 

It is constructed on the principle of the elas- 
ticity of the air. 


Fig. 1 — Air Pump. 
What is meant by its Elasticity ? 

Its elasticity is its constant tendency to ex- 
pand as pressure is removed. 
Is the air like other gases Elastic ? 

Like them, it is perfectly elastic, and as the 
pressure is removed indefinitely, it continues to 
expand indefinitely ; so that there has not been 
found a practical limit to its power of expan- 
What is the reason for this indefinite expansibility? 

It is accounted for by the principle of self- 
repulsion, which seems to be inherent in the 
molecules of all gaseous matter. 


What is the construction of the Air Pump? 

The air pump is simply .an exhausting 
syringe, whose piston is moved by a powerful 
lever, rendering it more efficient in pumping 
the air from the receiver placed upon the ptate 
of the machine. A description of the exhaust- 
ing syringe will, therefore, give the construction 
of the air pump. 
What is the Exhausting Syringe ? 

5 It consists of a hollow cylinder, to- 
which is fitted an air tight piston. Tin* 
cylinder communicates by a screw and 
pipe at the bottom with a vessel, gen- 
erally a receiver, from which the air is 
to be withdrawn. The piston carries a 
valve which opens upward, and con- 
nected with the pipe at the bottom, is 
another valve, also, opening upward. 
If, now, the piston be raised, a vacuum 
being formed in the cylinder, the air 
in the receiver expands, and instantly 
rushes into the cylinder, and passes out 
through the valve in the piston, as it 
descends against the bottom of the 
cylinder. It is obvious that a few 
strokes of the piston will so expand, 
Fig.~Ex-the air in the receiver as to produce 
syringe? there a virtual vacuum. 

The simple syringe arranged either singly or 
in pairs, and so adjusted as to be worked with a 
strong lever, having its cylinder in connection 
with a perforated, metalic plate, on which a re- 
ceiver may be placed, or to which any piece of 
apparatus may be screwed, constitutes the air 
What are the uses of the Air Pump ? 



It demonstrates the existence of weight in 
the atmosphere, and serves several useful purpo- 
ses in the laboratory and the arts. 
What is the numerical statement of the pressure of the 

Atmosphere ? 

It is generally stated to be fifteen pounds upon 
every square inch of surface; 14.6 pounds would 
be nearer the truer pressure. This is called 
one atmosphere ; thirty pounds would be two 
atmospheres, etc. 
What is the Cupping Apparatus or Glass ? 

It is a minature air pump. The principle of 
its action is illustrated by the hand glass on the 
plate of the air pump; the air being exhausted 
over a portion of the skin, the outside pressure 
of the air causes it to swell out and protrude 
into the glass. 
What is Gaseous Diffusion ? 

It is the remarkable property possessed by 
gases and vapors of passing into and mixing 
with each other, even against the law of 
What is the Law of Gaseous Diffusion ? 

The diffusive power of a gas varies inversely 
as the square root of its density. Example — 
hydrogen and oxogen as to their densities, are 
to each other as 1 to 16; their relative rates of 
diffusion are as 4 to 1, the square roots, re- 
spectively, of 16 and 1. 
Does not this Law admirably illustrate the wisdom of God? 

If no such law reigned in the world of vapors 
and gases, they would necessarily be associated, 
like oil and water, in the order of their specific 
gravities, so altering the condition of our at- 
anosphere as to make animal life on the earth 


impossible. " It is impossible to over-estimate 
the importance in the economy of Nature, of 
this very curious law affecting the constitu- 
tion of gaseous bodies; it is the principal 
means by which the atmosphere is preserved 
in a uniform state, and the accu inundation of 
poisonous gases and exhalations in towns and 
other confined localities prevented." 
What important distinction is here necessary ? 

The real diffusion of gases, must not be con- 
founded with another property they possess, of 
being transmitted through membranous dia- 
phragms, such as bladder, India rubber and 
gold-beater's skin. This is osmose, when dis- 
similar gases mix through porous diaphragms. 
What is Osmose ? 

It is the power possessed by gases of inter- 
mixing readily through partitions of mem- 
branous substances. 
What are the essential differences between Diffusion and 

Osmose ? 

Osmose, although partly due to the principle 
of diffusion, necessitates the presence of mem- 
branous diaphragm ; diffusion, on the contrary, 
takes place under all conditions in which gases 
are free to mix with each other. Diffusion 
purines 'the air before it enters the lungs; 
osmose corrupts it there with the poison from 
which diffusion had healthfully cleansed it. 
How is the Diffusion of Gases accounted for ? 

Diffusion takes place, whenever, the cohesive 
force of molecules is exceeded b} 7 the adhesive 
force which attaches them to the molecules of 
some other body. But gases have no cohesive 
force among their molecules, hence they readily 
intermix uniformly and in all proportions. 



How is Osmose of Gases accounted for? 

Osmose is partly due to the law of diffusion, 
even, through minute pores, but the force of 
adhesion, as exerted by the membranous parti- 
tions upon the gaseous molecules, plays an im- 
portant part in the process. The stronger this 
adhesion between the membrane and the mole- 
cules, the more rapid and abundant will be the 
osmose of the gases. They are condensed and 
liquified by the power of the adhesive force, 
and passing thus through the wet membranes, 
evaporate and re-appear on the other side as 
gases again. 
What is Absorption of Gases ? 

The diffusion of gases through liquids. This 
varies greatly for different liquids and gases, 
and for the same liquid and gas under different 
temperatures. Cold and pressure increase it; 
heat, on the contrary, lessens it. 
Are there now any Permanent Gases ? 

All the gases, even the most refractory, such 
as hydrogen and oxygen, have, at last, by a new 
and recent process, been liquified. This event 
constitutes a new era in Physics, and must lead 
to great results. 


Amorphism— Isomorph ism— Sublimation. 

What is Crystallization ? 

When certain bodies pass from the liquid or 
gaseous to that of the solid state, their mole- 
cules have the power to arrange themselves in 
regular geometrical forms. This is crystalle- 
zation, and the forms themselves are called 

What is Amoiphism ? 

Many substances do not possess this power to* 
ciystallize as they pass into the solid state; they 
are, therefore, amorphous, that isj without form, , 
as glass. 
Under what conditions may Crystals be pnoduced ? 

From melted substances slowly cooling — from' 
solutions as sugar — from the condensation of 
gases as in the production of nitric acid, and 
from the re-arrangement of the molecules of a 
solid, as the slow crystallization of railroad axles 
by constant agitation. 
How are Crystaline Bodies distinguished from each other? 

It is a general law that all crystalline sub- 
stances have their peculiar forms, and this 
peculiarity of form is dependent upon certain 
characteristics which are easily discovered in. 

To what classification does this give rise ? 

It divides all crystalline bodies into six: 

What are the Systems of Crystallization ? 


First — The monometric or cubic system. 

Second— The dimetric or pyramidal system. 

Third — The rhombohedral system. 

Fourth — The trimetric or right prismatic 

Fifth— The monoclixic or oblique prismatic 

Sixth — The triclinic or double oblique pris- 
matic system. 
What are the characteristics of these systems ? 

In every crystal certain straight lines may be 
imagined to be drawn through its centre from 
side to side, from end to end, or from angle to 
angle, around which it has grouped its mole- 
cules to produce its own peculiar form. These 
lines are called axes and are its characteristic 
What is the characteristic of the first system-? 

Three equal axes; all at right angles to each 
Of the Second ? 

Three axes at right angles, but one unequal — 
either longer or snorter than the other two. 
Of the Third ? 

Three axes, two of them equal, and at an 
angle of 00°; the third and principal one being 
at right aDgles to the other two. This is one of 
the most interesting and extensive of all the 
Of the Fourth. 

Three axes, all unequal and at right angles to 
each other. 
Of the Fifth? 

Three axes, which may be all unequal ; two 
of them at right angles to each other, while the 



third is oblique to one and perpendicular to the 
other of the first two axes. 
Of the Sixth ? 

Three axes, all of which may be unequal in 
length, and all oblique to each other. This is 
the form to which belong copper sulphate, 
bismuth nitrate, and potassa quadroxalate. 
What is Isomorphism?* 

Any two or more substances, which have the 
same f<ym of crystallization, are said to be 
isomorphous. These bodies are generally simi- 
lar in chemical constitution. They will replace 
each other in crystallized compounds without 
alteration of the crystalline figure. 
What is Dimorphism ? t 

Under different circumstances of high or low 
temperature, the same substance may assume 
different crystalline formes. This is dimor- 
phism. Carbon and sulphur are notable ex- 
What are the Isomorphous Groupes of elements ? 

There are eight : 

First — Sulphur, Selenium. 

Second — Magnesium, Calcium, Manganese, 
Iron, Cobalt, Nickel, Zinc, Cadmium, Copper, 
Chromium, Aluminum. 

Third — Barium, Strontium, Lead. 

Fourth — Platinum, Iridium, Osmium. 

Fifth— Tin, Molybdenum. 

Sixth— Sodium, Silver, Gold, Potassium, and 
perhaps Ammonium. 

Seventh — Chlorine, Iodine, Bromine, Fluorine. 

Eighth — Phosphorus, Arsenic, Antimony Bis- 
m u t h. 

*From isox equal and raorphe form, of*the Greek. 
tFrom dis two times and morphe form. 


It will be seen in another place, that these 
isomorphous elements are often likewise similar 
in their combining capacity— that is, in quan- 
Is there not a more general classification of all crystalline 

forms ? 

They are divided into primary axd secondary 
or derived forms. 
What is Primary Crystal ? 

It is one, which has been developed by equal 
additions on every part of it in accordance with 
the regular law. / 

What is a Secondary or Derived Crystal ? 

It is one whose development has been by 
unequal additions to the several parts of it r 
yet these additions being deposited in obedience 
to the usual geometric law of arrangement. A 
form different from the primary is thus pro- 
duced but obviously related to it. 
What striking Phenomena accompany Crystallization ? 

Increase of volume is a notable result; 1,000 
parts of freezing water expand to 1063 parts in 
crystals of ice. This force of expansion is so 
great as to shatter the strongest walls of iron. 
Heat is a constant result of crystallization, and 
occasionally flashes of light. 
What is the Goneometer ? 

The goneometer is an instrument for meas- 
uring the angles of crystals, in order to ascer- 
tain the system to which each may belong. 
What is Sublimation ? 

It is a solid passing into a gaseous condition 
and the reverse. 



Electro-Physics, Electro-Pbyseology, Electro-Diagno- 
sis, Electro-Therapeutics, Electro-Medicine, 
Electro-Surgery, Electro-Therapeutical 
Apparatus, Special Applications 
of Electricity. 

What is Magnetism ? 

It is that branch of Physics which treats of 
the phenomena of magnets, both natural and 
Js anything known of the Nature of this force? 

Nothing; it is a form of electricity. 
What is the Natural Magnet? 

It is the black oxide or magnetic iron ore, 
crystalized in cubes, and one of the most valua- 
ble of iron ores. A fragment of this oxide, if 
properly suspended, will turn one side to the 
North, and the opposite to the South. It, there- 
fore, manifests polarity. 
What is Polarity ? 

Polarity is a general term, and in this sense 
means simply two opposite states or conditions, 
whatever they may be. Hence there is mag- 
netic polarity, electric polarity, polarity of light, 
and the polarity of chemical affinity. It is an 
essential principle in all Physics. 
What is an Artificial Magnet? 

Bars of iron and steel can be made magnetic 
by simple contact with a natural magnet; and 
then again, may impart their polarity to other 
pieces of the same metal. 



What is the Attractive Force of a Magnet termed '' 

The attractive force of a magnet is called its 
Magnetic Force. 

What are the Poles of a Magnet? 

They are the two opposite points, where its 
magnetic force is most strongly exerted. 
What is the general Law of Polarity ? 

Like poles repel each other ; unlike poles 
attract each other. 
What is Magnetic Induction ? 

It is the power which any magnet possesses 
of imparting its magnetic force to other bodies 
in contact with it or in its neighborhood. Soft 
iron loses its induced magnetism on the re- 
moval of the inducing magnet, but steel retains 
it permanently. 


What is Electricity ? 

It is a subtle agent of whose nature, we yet 

know nothing. Like heat and magnetism it is 

a mode of motion of the molecules. 

How is Electricity excited? >■ 

If a rod of glass, or piece of sealing wax he- 
rubbed with a warm silk handkerchief, a crack- 
ling noise will be heard, and if it be dark, 
sparks will appear. This is frictional or Frank- 
linic electricity. 
What are Electrics ? 

Any substances that manifest electrical ex- 
citement by friction, such as the glass rods and 
sealing wax above, are termed electrics. 
What are Conductors and Non-conductors of Electricity? 

Some substances give ready passage to elec- 
tricity; those are called conductors; there are 
other bodies that retard or almost prevent its 
passage; these are non-conductors. The last- 
are also called insulators. 

What are the lies t Conductors of Electricity? 

The metals, charcoal, the earth, all liquids, 
except oil, moist air, water and the human 

What are the best Insulators? 

Gum shellac, gutta percha, sulphur, sealing 
wax, glass, all resinous bodies, silks, feathers. 
hair, dry air, dry wool and baked wood. 
"In how many forms does Electricity appear to manifest 


In two forms— vitrious and resinous electri- 
city. Franklin named them positive and nega- 
tive electricity, distinguishing them by the 
signs (-{-) and ( — ■) plus and minus. 
What is the general Law of Electricity ? 

Like electricities repel each other; unlike 


attract each other. This is the polarity of 


What is Electrical Tension? 

The degree of electrical excitement in any 
body is its electrical tension. I s release is 
called DISCHARGE. 
What is Electrical Induction ? 

It is the power which an electrically charged 
body possesses of distributing the electrical con- 
dition of other bodies at a distance from itself. 
It is partial conduction, or a preparation for 
passage from one body into another. The 
molecules in all substances are more or less sus- 
. ceptible of electrical excitement. 
What is the Velocity of Electricity in Motion ? 

Some have estimated its velocity of motion 
: as high as 280,000 miles per second; but prac- 
tically the United States Coast Survey found it 
to pass through iron wire with a velocity of 
. only 20,000 miles per second. 
How is Frictional Electricity obtained ? 

Usually from an apparatus called the elec- 
trical machine. It may now, however, be 
obtained in far greater abundance and conve- 
nience from a Ruhmkorff's coil, an electro- 
magnetic apparatus yet to be described. 

What is a Leyden .lar ? 

It is a glass vessel having a wide mouth, 
more than one half of whose internal and ex- 
ternal surface is lined with tin foil. Ttie 
mouth is closed with a cover of baked wood, 
through the middle of which passes a metalic 
rod, the upper end terminating in a ball, and 
the lower in a chain hanging down in contact 
with the foil on the bottom of the jar. 



Fisj. 14.— New Electrical Battery. 

What is the Electrical liattery ? 

It is a combination of Leyden Jars, so arranged 
that they may be all at trie same time charged 
from the electrical machine, and all at the same 
moment discharged. 
"What does Figure 14 represent ? 

It illustrates an improved battery of Leyden 
Is Franklinie or Frietional Electricity of any Therapeutical 


This form of electricity is no longer used 
medicinally, having been superseded by the 
more convenient and efficient applications of 
galvanic and faradie electricity. 
What is Galvanism or Galvanic Electricity? 

It is the electricity produced by the chemical 
action of two or more dissimilar substances 
upon each other. The same form of electricity 
is sometimes called Voltaic electricity. 


What simple Experiment illustrates the production ol Voltaic 
Electricity ? 

Place a silver coin on the tongue, and a piece 
of zinc underneath it ; when the metals are 
made to touch each other, the tongue will ex- 
perience a -peculiar thrill, the mouth a metalic 
taste, and theeyes, if closed, a sensation of light. 
How does Galvanic Electricity differ from Franklinic 

Electricity ? 

Franklinic electricity is intense in action, 
and quick to seek equilibrium by discharge ; it 
does not How in a steady stream, but leaps to 
its object like a river over a precipice. Gal- 
vanic electricity, on the contrary, with little 
intensity flows quickly in a constant, unbroken 
Is not this distinction very important ? 

It is; for it is the sole explanation of the 
superior practical utility of Galvanic electricity 
in Medical Surgery and Arts. 

What Principle forms the basis of the Science of Galvanic 
Electricity ? 

Two solid, conducting bodies, usually metals, 
being immersed in a compound liquid, which 
acts unequally upon one of them, disturbs 
electrical equilibrium. One of the metals 
becomes positively excited and the other neg- 
atively; this is the polarity of Galvanism and 
the basic principle of the science. 

Which is the Electro-positive metal or body, and which the 


The metal most easily acted upon, is termed 
the electro-positive metal, and the other the 

What is the Power thus generated, called ? 


What is the classification of bodice, which arc capable of 
producing the E'ectro-motive Force ? 
All the elementary substances may be so 
arranged in a series, that any one above in the 
series, shall be negative to any that is below, 
and any one that is below shall be positive to 
any above. The more remote they stand from 
each other, the more powerfully will their con- 
tact be productive of electricity. . 

What substances are most in use for this purpose, and what 
is their relative arrangement ? 

Carbon, Antimony, Gold, Platinum, Silver,. 
Copper, Tin, Lead, Iron and Zinc. 

Zinc and charcoal are, therefore, the most 
powerful generators of electricity in such a 
combination, and copper and tin among the 

What are the Essential elements of a Galvanic Combina- 
tion ? 

There must be present, at least, three ele- 
ments, one a solid, the second a fluid, and the 
third either a solid or a fluid. 

What is a Galvanic Circuit? 

When the elements are so arranged that there 
is a continuous flow of positive electricity in 
one direction, and of negative electricity in the 
opposite, a galvanic circuit is formed. 
Where will be the strongest manifestation of Electrical. 

Action ? 

At the point where the two currents meet- 
where the poles of the combination are nearly 
in contact. 
What names are given to these Poles ? 

The free end of the wire attached to the zinc- 
plate is called the negative electrode, the 


extremity of that attached to the copper or 
carbon plate, the positive electrode. It must 
be remembered, however, that the zinc plate is 
positive, and the copper or carbon negative. 
When is a Galvanic Circuit said to be closed? 

When the electrodes are in contact, the cir- 
cuit is said to be closed. The current still flows, 
however, but gives no sign. 

What distinct names are sometimes given to the Poles of a 
Galvanic combination ? 

The positive pole is sometimes called the 
anode, and the negative the cathode, from two 
Greek words, ana upwards and oidos a way, kata 
downwards and oidos. The first belongs to the 
positive wire and the second to the negative. 

The term pole, so often applied above, must 
not mislead the student into the idea, that 
attraction and repulsion are properties of the 
electrodes in the galvanic cirtuit. Faraday 
proved the contrary. 
Do both plates or metals of a circuit, serve to generate 

Electricity ? 

One— the positive — acts on the generator, the 
other — the negative- — as a conductor of electri- 
city. The zinc plate is the positive generator; 
the copper or carbon the negative conductor. 
What is a Galvanic Cell? 

A single combination of the essential ele- 
ments of a circuit. 
How may the quantity of galvanic Electricity be increased'.' 

By enlarging the plates of a cell. 

How may the Tension or Intensity of galvanic action be 
' ased ? 
T>y multiplying the number of the cells. This 
•constitutes a compound battery. 


What are the principle Galvanic Batteries now in use ? 

Smee's, Daniel's, Grove"s and Bunsen's, and the- 
Cromic Acid Battery. 
What is Smee's Batter}- ? 

It is-the simplest in use. Its combination is 
two metals and one liquid, the metals being 
zinc and silver, and the liquid a weak solution 
of sulphuric acid and water. The silver plate 
is coated with platinum, and the zinc with 

What is Daniel's Batiery ? 

It is the battery of best sustained action. The 
combination is two metals and two liquids ; 
copper and zinc, diluted sulphuric acid, and a 
saturated solution of copper sulphate. 
What is Grove's Battery ? 

This is the battery of grea'est galvanic 
action. Its combination is two metals and two 
liquids, zinc and platinum, weak sulphuric acid 
and strong nitric acid. 

Fig. 17 rf presents an effi- 
cient Bunsen's Battery com- 
posed of two cells, large glass 
jars, each containing five 
carbon and five zir.c ele- 
ments, with windless and 
crank for raising and lower- 
ing. All of the apparatus 
described in these pages, 
are made in the highest per- 
fection by Hall & Benjamin, 
of New York. 
Fig. 17.— Bunsen's Battery. 
What is Bunsen's Battery ? 
Bunsen's is a modification of Grove's, mak ins[_ 


it cheaper, but a little less powerful, by substi- 
tuting carbon plates for the more expensive 
What is the Chromic Acid Battery ? 

This is a modification of Bunsen's battery. 
The zinc is amalgamated, and the jar filled 
with a saturated solution of salt or sulphuric 
acid diluted with twenty parts of water. The 
porous cup is filled with a solution made by dis- 
solving one pound of potassic bicromate in ten 
pounds of hot water, and when cold adding five 
pounds of strong sulphuric acid. This is a con- 
venient and inexpensive battery and much used. 


Faraclaism, Faradic Electricity, or Electro-Magne- 
tism and Magneto-Electricity. 

What is Faradic Electricity or Faradaism ? 

This is identical with electro-magnetism, 
which is that form of magnetism that is pro- 
duced by the action of the electric current. 
This was discovered by Faraday, in 1831. 
What was the extent of Faraday's Discovery? 

He discovered, as Franklin had done in the 
case of atmospheric and common electricity, 
the identity of common electricity with gal- 
vanism, magnetism and thermo and animal 
What was the extent of U\rsted's Discovery ? 

(Frsted's discovery was limited to the effects 
■of .the electric current on needles, that were 
already magnetized. He first revealed the 
powers of the uninterrupted current. 


What is Electro-Magne- 
tism ? 

It is magnetism de- 
veloped through the 
agency of electrical 

Fig. 20.— Electro-Magnet, sustaining 150 His. 
Is not this uninterrupted current the great distinction 
between Electricity and Electro-Magnetism ? 

Franklinic electricity is capable of a quiet 
current; and galanic electricity, previous to 
the time of (Ersted, was limited to the action 
of a broken current between the electrodes; but 
electro-magnetism is such, only in virtue of its 
uninterrupted currents. 

What are Induced Currents ? 

They are currents which are produced by the 
action of magnets or other electro currents. 
They constitute electro-magnetism. 
What is the Mode of their Production ? 

When two conductors, as 
iron wires, are arranged par- 
Jallef, and near each other,each 
induces an opposite current in 
the other. If the circuit be 
lg * '''Thvit^' 10 broken again, another current 



passes in the same direction as the first or pri- 
mary current, inducing another secondary cur- 
rent; so that at each close and break of the- 
circuit, rapidly made, the electrical intensity is 
powerfully increased. A current of electricity 
passing through one turn in a coil of wire, in- 
duces two secondary currents in all the other 
turns of the coil. The effect of the latter miist, 
therefore, be added to the prinlary. This was 
Faraday's discover}^ and hence induced electri- 
city is called Faradaism. 
What is shown by the Magic Circle ? 

An e'ectric current being sent around the 
coil the united pieces of soft iron become pow- 
erfully magnetized, and are teM together with 
great force, as long as the current continues. 

What is an Induction Coil? 

If several hundred feet of stout copper wire 
be wound closely around a hollow cylinder, and 
another finer wire of several thousand feet,, 
both carefully insulated with silk wrappings, 
be wound upon the first wire in a secondary coil, 
a current sent through the first, and rapidly in- 
terrupted, will induce secondary currents in the 
other wire of such intensity, as to manifest all 
the phenomena, such as sparks and shocks of a. 
jwwerful electrical machine. 

Can the Magnet induce these primary and secondary cur- 
rents as well as Electricity ? 

It can, and a powerful steel magnet is capable 
of intensifying the currents to such a degree, 
by secondary currents, as to exhibit all the 
phenomena described above. 
What is the mode of its action? 

Let the keeper or armature of a powerful steel 


magnet, be wrapped with a very long insulated 
coil, and then be so adjusted as to revolve by 
multiplying wheels with great velocity in front 
of the poles of the magnet. This reverses with 
equal rapidity, at each half revolution the in- 
duced polarity of the keeper, giving rise, in 
the coil, to powerful magneto-electric currents. 
This is magneto-electricity, and another source 
of Faradaism. The apparatus is called the 
Magneto-electric Battery. 

Is it not highly probably that this whole phenomenon of 
Dynamic Induction, is only an altered direction of the 
electric current, producing what is called Magnetism ? 

This is Ampere's theory; and it is remark- 
able that the electric current, contrary to the 
action of all the other physical forces, induces a 
motion always at right angles to its own line 
of direction. This altered direction of motion 
is magnetism, and the only difference between 
electricity and magnetism. 
How may Faradaism, therefore, be again briefly defined ? 

It is the magnetization of the coils or helices,* 
inducing thereby all the phenomena of elec- 

Will not the same magnetization take place in an iron rod 
or a bundle of such rods — permanently if steel, and tem- 
porarily if soft iron— placed in the hollow of a helix in 
connection with an electro-battery ? 

Such rods will be intensely magnetic so long 
as the connection is maintained, but cease to be 
so as soon as the connection is broken. This 
principle or adjustment is very important in 
the construction and action of electrical appa- 
What is Neef 's Induction Coil ? 

-The word helix is Greek, meaning a cork screw. 

66 student's manual of 

Dr. Neef's coil is a happy combination of 
Electro-magnetism and Magneto-electricity. 
Insert into the hollow cylinder of the induction 
coil a bundle of soft iron rods, and upon their 
upper extremity, adjust a plate of soft iron, 
which can be alternately attracted to and freed 
from the rods as the interrupted currents pass 
through the coils, thus producing a rapid auto- 
matic closure and breakage of their currents. 
This is Neef's coil, an invention, which so im- 
proved the apparatus of Electro-therapeutics as 
to raise it at once to the dignity of a special 

Fig. 13. — Ruhmcortf 's Coil. 
What i.s Ruhmcorff's Coil? 

This apparatus, is nothing more than Neef's, 
with an improved insulating material or fixture 
for the coils. It is capable of yielding long 
electric sparks, and most deadly discharges of 


What is the Galvenometer ? 

It is an instrument for measuring the'intensity 
of electric currents. The principle of it is, as 
already stated, that a current of electricity will 
deflect a magnetic needle at right angles to the 

What was the extent of Sir Humphreys Davy's Discovery 
in Electro-Physics ? 

He established the fact that the electro-current 
will induce magnetism in pieces of iron and steel 
not previously magnetized. 
What was Dr. Henry's Discovery? 

He discovered the method of constructing effi- 
cient electro-magnets. This invention made 
way for the telegraph. 


What is Electro-Physiology ? 

It is that branch of Electro-Physics which 

considers the vital relations of electricity in all 

its forms, to the functions of the living animal. 

It includes, also, in a special sense, what is 

known as ancient electricity. 

Under what particular heads may the student of Electro- 
therapeutics study this suhjeet ? 

First— Its general effects upon the nerves and 

Second — Its action on the brain and spinal 

Third — T ts action on the nerves of specnl 

Fourth— Its action on the muscles, both vol- 
untary and involuntary. 

Fifth — Its tonic and neutritive effects upon 
the svscem. 


Sixth — What are the different effects on these 
several heads of Faradic Electricity. 


What is Electro-Diagnosis ? 

It is the application of galvanic, and faradic 
electricity to the detection of special diseased 
conditions. This art is rapidly groAving in im- 
portance, with the increasing use of electricity 
in Medicine. 
Upon what does its successful application depend ? 

It depends upon the exercise of much acute 
observation, careful manipulation, and more 
especially upon the important faet, that the 
effects of electricity are sensibly modified by 
the presence of disease in any organ. 
"What names are given to these Diagnostic signs ? 

They are called quantitative and qualita- 
tive reactions of Electro-therapeutics. The 
first is sometimes termed the reaction of degen- 
eration, and consists in an alteration in the 
order of occurrence of the contractions. 


What is embraced in the term Electrization ? 

It includes every form and detail of the ther- 
apeutical applications of electricity. 
How many and what are the chief methods of Electrization ? 

There are four of these methods : 

First — Localized Faradization. 

Second — Localized Galvanization. 

Third — General Faradization. 

Fourth — Central Galvanization. 


What is Local Faradization ? 

It is the art of limiting the effects of the 
faradic current to certain organs and tissues. 
What is Local Galvanization? 

It appears to be the art of so applying gal- 
vanic electricity, as to produce certain effects, 
and no others in- any special organ or tissue. 
In other words, it is the art of making the 
current act at will, as a sedative, stimulant or 
tonic, etc. 
What is General Faradization ? 

It is such an application of faradic electricity 
as will bring all the internal organs and tissues, 
and the entire surface of the body under the 
influence of the induction current. For general 
electrization the faradic current is always pre- 
ferred; galvanization is too potent in its effects. 

What is Central Galvanization ? 

It is that method of treatment by which the 
whole central nervous system— brain, sympa- 
thetic nerves and spinal cord— are brought 
under the influence of the galvanic current. 

This application requires a familiar knowl- 
edge of Electro physics, with a deep insight 
into both the functional and structural derange- 
ments of the nervous system. 


What is Electro-Surgery ? 

Electro-surgery is that branch of Electro-ther- 
apeutics, which treats of electrolysis, and the 
processes and methods of galvano-cautery. 

What is Electrolysis ? 


KX< llK.vr ,S MAM 

In a wider sense, according to the etymology 
of the word, electron and luo to set free by elec- 
tricity, electrolysis means the decomposition of 
any compound substance by electricity. In 
surgery it signifies the same application of elec- 
tricity to any diseased tissue or structure of the 
living organism — such as tumors, moles and 

To what altered structures has the Electrolytic process been 
applied with more or less success ? 

It has been used in erectile and cystic tumors 
with remarkable success, in goitres, fibroids, 
cancer, ovarian tumors, varicose veins, and 
What is Galvano-Cautery ? 

It is the process of cauterization by a resisting 
wire heated by the galvanic current. The elec- 
tricity is not applied as in electrolysis, to the 
body or diseased part, but to the wire only. 

What advantage has Galvano cautery over the actual cau- 
tery ? 

The operator with the former has not only a 
more complete and prolonged control of the 
process, but he has access to parts and a choice 
of methods wholly out of the reach of the actual 
cautery. The wound, too, heals quicker, has 
less tendency to pyaemia, and all fear of hemorr- 
hage is well nigh set aside. 

What metal is alone suited for use in Galvano cautery, and 

Platinum is the only metal suitable to this 
process. Of all the metals, except mercury and 
lead, it opposes the greatest resistance to the 
passage of the current, and the greater the re- 
sistance the greater the heat. 

Does not the proper application of Galvano-eautery require 
great care in the use and preparation of instruments? 
It is obvious that in this department of Elec A 
tro-therapeutics, the surgeon, who has no ex- 
perience in diagnosis, no love of detail and no 
skill or tact in the management of electrical 
apparatus, would do better in the old ruts of 
the profession. But with all due allowance, it 
is not extravagant to write, that after anaesthe- 
sia, galvano-eautery is the century's noblest 
contribution to surgery. 


What Faradic and Galvanic Batteries for Electro-Thera- 
peutical use can be recommended ? 

Those sold by Hall & Benjamin, of New York, 
are among the best in use. Their Faradic 
Battery, No. 1, is chiefly designed for the use 
of physicians in diagnosis, and cases requiring 
the ordinary applications of electricity. Battery 
No. 3, of the same company, is a more complete 
and powerful instrument, and hence of larger 
application in a general medical prctice. 
How may ihe value of the Electro-motive Force of the 
various batteries used in Electro Medicine be compara- 
tively estimated ? 

The ordinary Daniell element, consisting of 
zinc and copper, immersed in a solution of sul- 
phuric acid and copper sulphate, yields an elec- 
tro-motive force, which maybe represented by 1. 
What then will represent the strength of the Bunsen 

element ? 

This element, formed of zinc and carbon, 
immersed, the one in dilute sulphuric acid, and 
the other in stroag nitric acid, will have an 
electro-motive force of 2. 



What is the Strength of the Chromic Acid element ? 

This element, zinc and carbon, in a solution 
of sulphuric acid and bichromate of potash wi 1 
give a force of 14. 
What wi'l represent the Smee Cell? 

This cell, composed of zinc and platinum, in 
solution of dilute sulphuric acid, will yield an 
electro motive force of 8. 

What is the essential quality of a Galvanic Battery for 
Medicinal purposes ? 

It is constancy of action, and this is best 
obtained in two fluid cells. 
Why do the two Fluid Cells best achieve constancy. 

Because the arraugement of two fluids effect- 
ually presents the polarization of the battery; 
it depolarizes it. 
When is a Battery siid to be Polarized ? 

It is polarized, when there is such an accu- 
mulation of hydrogen at the negative plate, 
and of oxygen at the positive, as to check or 
anihilate the current. 
What other name is sometimes given the Galvanic Battery? 

This battery is frequently called the Continu- 
ous Current or Constant Current Battery. 

What are frequent synonims of the Faradic Battery ? 

It is often called the Electro-magnetic, the In" 
duced Current or Interrupted Current Battery. 
What are the Laws of Dynamic Electricity? 

First — The strength of the current is directly 
as the electro motive force. 

Second — The streng h of the current is in- 
versely as the resistance. 

Third — The resistance is inversely as the 
transverse diameter of the wire. 

Fourth — Force generated by the current is 
directly as the resistance. 

These are Ohm's Laws of Electro-dynamics. 


Whft must guide the Profession in the use of Weights and 

Measures ? 

So long as the United States Pharmacopoeia, 
holds to the weights and measures of the English 
system, it must be the practical system of the 
profession in this country. 
From what are the Apothecary Weights derived? 

From the pound Troy. 
What are its Denominations and Symbols ? 

T4ie pound lias the symbol (lb) from the Latin 
Libra. The (/?) from the Latin uncia. The 
drachm (3) is from the Latin drachma. The 
scruple (3) from scrupulum, and the (gr.) from 
the Latin granum. 
Are the Pound, Scruple, an 1 Drachm used in t'le Pharma- 


They are all omitted, and weights wholly 
expressed in ounces and grains. 
Are not the Drachm and Scrapie used in written Formulas? 

They are; and these symbols have been some- 
times so carelessly written, as to be mistaken 
the one for the other, causing fatal results. 
From what are the Measures derived ? 

From the old wine gallon. 
What are their Denominations and Symbols? 
Gallon, symbol C. from Latin congeus. 
Pint, symbol 0. from Latin octarius. 
Fluidounce, symbol ff. from Latin Fluiduncia. 

Fluidrachm, symbol fS.from Latin Fluidrachma. 
Minim, symbol M. from Latin minimum. 

How are the Ounce and Drachm of this measure distin- 
guished from those of the Weights? 
The letter f. is always written before these 


What tables indicate the relative values of the Weights and 
Measures, respectively? 

rb.=125=963=2883=5760 grains. 

l|= 83= 243= 480 grains. 

13= 33= 20 grains. 

1 C.=80.=128f l=1024f 3=61440 Mm. 

10= 16f== 128f3= 7680 " 

Iff— 8f3= 480 " 

If 3= 60 ' : 

Do these Weights and Measures used in Great Bri'ain cor- 
respond exactly with ours? 

They do not, and physicians in this country 
should be careful in writing prescriptions from 
English authorities. They use the Imperial 
pound and gallon. 
In writing a Prescription how are the Quantities expressed? 

They are written generally, in the symbols 
of the Roman table, the fractions excepted. 

Are they not sometimes written in the Latin numeral adjec- 
tives ? 

They are, and in order to do this correctly, it 
is necessary for the student to know something 
of the Latin language. 

Let the following Prescription he written out in both forms. 
IL — Zinci Sulphatis, grana tria. 
Aluminis, gratia sex. 

Aquae rosa\ uncias duas. 

M. fac. collyrium. 

In the symbols— $. — Zinci Sulphatis. gr. iij. 
Aluminis, - - gr. vj. 
Aquse rosse, - - |. ij. 

The symhol of the denomination is always 
written before that of the quantity. 
How are the Fractional quantities expressed ? 

The Roman table has no fractions; it is usual, 
therefore, to express a half by the abreviation 
(ss.) from the Latin semi, a half. Other frac- 
tions are written in the Arabic characters as 
j or xr. 

What domestic measures are patients directed to use as 
equivalents of the ounce, drachm and minim? 

The teaspoon as equal to lf3. 

Dessertspoon as equal to 2f3. 

Tablespoon as equal to 4f3. 

Wine glass as equal to 2R. 
Are these equivalents strictly leliable ? 

They are not, and several fatal results have 
followed this loose method of prescribing power- 
ful drugs. 

What should be recommended to families as better and 
safer ? 

Physicians would do well to advise families 
under their care, to provide themselves with a 
crrrectly graduating glass — American not En- 
Is it always safe to prescribe fluid medicines by drops? 

This practice is often dangerous; for the 
value of a drop depends upon several uncertain 
conditions; temperature, density, shape of a 
vessel's mouth, and steadiness of hand. 
What is Dr. Squibb's method of measuring by drops potent 

or undiluted liquids? 

He introduced for this purpose a pipette 

S'l'UIEVL' S MAM \ |. ill' 

graduated to minims ; a little instrument 
"whose convenience, commends it to every prac- 
■tioner and family. 
What is the action of the Pipette? 

It is a small glass tube, open at both ends, 
and tapering to a point at one extremity. The 
tapering point being immersed in any fluid, re- 
ceives a considerable portion of it by capillary 
attraction, which is retained in the tube by 
closing the upper end with the thumb. After- 
wards, the fluid may be discharged, drop by 
drop, on the cautious removal of the thumb. 
This instrument may be bought of any druggist. 

The Language and Grammatical Structure of 

Are there good reasons why Medical Prescriptions should 

be written in the Latin language ? 

The reasons for this timedionored custom are 
many and obvious. The Latin is a dead lan- 
guage, fixed forever in its words, rules and 
structure, yet an object of continued study and 
acquisition to the educated and scientific in all 
civilized countries. This it must be as long as 
human learning shall endure. It is, therefore, 
a universal language, and eminently fitted to 
become the vehicle of systems of knowledge 
addressed to all civilized people. Scientific 
men labor for the benefit of the race, hence it 
is projoer that they should be able to speak to 
mankind in a language, as universal as the 
Latin, and crystalized as it is in classical purity 
and excellence. These remarks are as perti- 
nent to the Latin nomenclature of science as 
to the language of prescriptions. 


What, therefore, is the Student's first step in the art oi 
elegant and correct prescription writing? 

He must first acquire a respectable know- 
ledge of the Latin language. This learning 
will likewise fit him to study with advantage 
the whole subject of medicine, both as an art 
and a science. 
What is a Medical Prescription ? 

A prescription maybe given verbally; many 
a one is written that prescribes no drug, and 
asks nothing of the apothecary. It may be 
defined; a formula written or spoken by a phy- 
sician directing the compounding and adminis- 
tering of medicines, or the use and application 
of any remedy for the sick. Technically the 
word requires something to be written, coming 
from the Latin prse, before and scripUo, written. 

Into how many parts is a Formula divided ? 
Into five: 
First — The head. 

Second — The medicines and their quantities- 
Third— The directions to the pharmacist. 
Fourth — The directions to the patient. 
Fifth— The date and signature. 

What constitutes the Head ? 

The letter h\ marked as it is making it a 

special symbol. It comes from the imperative 

Lati» verb, recipe, meaning take. 

How is the second part always written and in what di- 

The names of quantities of ingredients are- 
always written in Latin. 

First — Is the basis or the active agent. 

Second— The auxiliary, promoting the ac- 
tivity of the basis. 


Third — The corrective, modifying the action 
of the base 

Fourth — The vehicle, to give form and taste. 
"What old Latin aphorism expresses briefly and pointedly, 

the design and power of a Formula ? 

Curare cito, tute ct jucunde — To cure quickly, 
safely and agreeably. 
How are the quantities indicated? 

Either by weight, as solid, or by measure, as 
liquid, unless written in the metric system, 
where all is in weight. 
How is the Third part of the Formula written ? 

The directions to the apothecary are also 
written in Latin. 

How is the Fourth part written ? 

The directions to the patient are always, in 
this country, written in plain English. This 
part is called the s'gnature abreviated into S. 
or Sig. from the Latin, signa a sign. 
Should not the directions be written with great care ? 

The physician will write his instructions full 
and clear as to dose, time, method of taking the 
medicine, and any other information important 
to the patient. Mere verbal directions should 
not be the rule, and if an ingredient is a dan- 
gerous poison, it should be so marked generally. 
Should every Formula receive the Physician's signature. 

Every prescription should be signed by the 
writer, and in large cities, even his address and 
office hours might be added. A little reflection 
will show the reason for this. The date is, also, 
as important as the signature. In laying down 
rules for the guidance of the student here, it must 
be taken for granted that he has some know- 
ledge of Latin declensions, the rules of syntax, 


and the naraes of the numeral adjectives and 
adverb?. If he has none, he should go at once 
to the Latin grammar and learn them. 

What is Rule First in the proper structure of a Prescrip- 
tion ? 

The noun expressing the name of the medi- 
cine, is put in the genitive case, if the quantity 
of it, is also, expressed. 

Example — R. — Extracti opit. gr. v. 
What is Rule Second ? 

If no quantity is expressed, but only a nu- 
meral adjective follows, the noun is put in the 
Example — R — Ovum unum. 

What is Rule Third? 

The quantity is put in the accusation case, 
governed by the imperative verb recipe. 

Example— R. — Acidi tanici. drachmas dua?. 
What, is Rule Fourth ? 

The adjectives agree with their nouns in 
gender, number and case. 

Example — R. — Vitelmjm ovi unum. 

The accusative of the quantity can always be 
avoided by using the Roman symbols. The first 
rule is in constant use, and increases the im- 
portance of the genitive. 
What is Rule First relating to the Genitive ? 

All Latin nouns of the first declension end in 
a, and form their genative singular in a'. 

Example — Jalapa, genitive Jalapse. 
What is Rule Second ? 

All Latin nouns of the second declension, 
ending in us, um, os, and ox, form the genitive 
singular in i. 

Example — Syrupus, genitive syrupi, Opium, 

80 student's mantai, of 

genitive, opii, Htematoxylon, genitive, hsema- 
toxyli, Scyros, genitive, scyri. 

What is Rule Third relating to the Genitive ? 

All other nouns, important here, no matter 
what their nominative ending may be, form 
the genitive singular in s. 

Example — Calx, genitive, caleis; sulphas, 
gen. sulphatis; fructus, gen. fructus; chloral, 
gen. chloralis. 

Greek words from such genitives, as these; 
asclepias, genitive, aclepiadis; anthemis, gen. 
anthemidis ; hydrastis, gen. hydrastis. But be- 
sides hydrastis, there are several other names of 
common use, which do not change their nomina- 
tive to form the genitive; as amyl, gen. amyl; az- 
edarach, berbesis; buchu; cajuputi; cannabis; 
catechu; coca; condarango ; cornus; curare; 
fructus; digitalis; kino; quercus ; sassafras; 
sago; sinapis and spiritus. 

What two Rules are important for the formation of the 

Accusative ? 

Rule First is, Latin nouns ending in a, of the 
first declension, are feminine, and form their 
accusative singular in am, and the plural in as. 

Example — Pilula, gen. pilulse, accusative, 
singular pilulam, plural pilulas. 

Rule Second is, Latin nouns of the second 
declension, ending in um or us, form their accu- 
sative singular um. The accusative plural of 
those in us, which are masculine, is os, of those 
in um, neuter, a. 

Example — Ovum, accusative, singular, ovum, 
plural, ova : syrupus, accusative: syrupum, plur. 
How do the Adjectives form their cases; 


Like the nouns, for Latin adjectives, unlike 
the English, have declension. Of the numeral 
adjectives only three of constant use, are de- 
clinable; they are unus, one, duo, two, and 
tres, three. 

Mas. Fern. Neut. 

Norn unus una unum 

Gen unius unius. . . .unius 

Accu unum unam 


Nom duo duae duo 

Gen duorum .... duarum . . .duorum 

Accu duos duas duo 

Nom tres tres. . . . tria 

Gen trium trium triuni 

Accu tres tres tri-i 

In what mood and tense are the verbs used ? 
In the imperative mood, present tense. 

What Prepositions are used in writing Prescriptions ? 
A few only ; they are ad, to ; ana, of each ; 

cum, with ; and in, meaning into. Add and in 

govern the accusative cum the oblative, and 

ana, a Greek word, the genitive. 

What is the Latin Rule for the Ablative case, of the 1st and 
2d Declensions ? 

In the 1st and 2d declensions, the ablative 
case singular, ends in the 1st in a, in the 2d in 
o; the plural of both, in is. 

Having these few brief rules properly digest- 
ed, the intelligent student, with a little practice, 
will be able to write any Medical formula, with 
elegance and propriety. He should not rest 
satisfied short of this accomplishment. 

The present tendency of the profession, is, 
decidedly towards simplicity, not only in the 



number of the ingredients of a prescription, 
but in the verbiage of its directions. In Great 
Britain, physicians still write, both the direc- 
tions for the pharmacist, and those for th« 
patient in Latin; among us. the directions for 
the ayothecary alone, are in Latin, and this, for 
obvious reasons, is a great improvement. I 
shall, therefore, refer here to such phrases and 
words, only as are in most frequent use among 
educated American physicians. 

What abbreviated Words and Phrases, beginning with the 
letter A, are important ? 

They are : 

ad up to 

ad libitum ad lib . . ... at pleasure 

adde add add thou 

ana aa of each 

aqua bulliens aq. bull. . , ..boiling water 

aqua distillata aq. dist distilled water 

What beginning with B ? 

bene. well 

bis in dies bis ind twice daily 

bull iat bull let boil 

What beginning with C ? 

cape cap let him take 

capsula caps a capsule 

ceratum cerat cerate 

charta chart a paper 

cochleare magnus.coch. mag. a tablespoon 
cochleare parvum..coch. par v. .a little spoon 

collyrium colly r an eve wash. 

collutorium collut a mouth wash 

compositus comp a compound 

congius c a gallon 

cortex. cort bark 

cum cum with 


What beginning with D? 

decoctum decoc a decoction 

dilute dil dilute thou 

dimidius dim one-half 

divide d. and div. .divide thou 

dividendus dividend. . .to be divided. 

dividatur in partes , . le } j* h . e divi ; 

ecmales a. in p. «q. dedintoequal 


dosis dos a dose 

What beginning with E? 

emplastrum emp a plaster 

enema enem an enema 

extractum ext an extract 

What beginning with F ? 

fac f make 

fiat ft let be made 

riant (plural) fn t let them be made 

filtrum ... fil a filter 

filtra (verb) filt filter thou 

fluidus flu a fluid 

Wba* beginning with G ? 

gargarisma garg a gargle 

gittta, guttse gtt a drop, drop? 

guttatim guttat drop by drop 

What beginning with H ? 

haustus haust a draught 

hora h. or hor ... an hour 

What beginning with I ? 

in dies ind daily 

infusum inf an infusion 

injectis inj an injection 

What beginning with L ? 

lac . . lac milk 

&t student's manual of 

lintium lint .lint 

liquor liq a solution 

lotio lotio a lotion 

What beginning with M ? 

magnus mag large 

massa mass a pill mass 

misce m mix thou 

mistura mist a mixture 

mucilago mucil a mucilage 

What beginning with N ? 

numerUS, numero. .no a number, in number 

What beginning with ? 

octarius o a pint 

ovum ov an egg 

What beginning with P ? 

pars par a part 

partes equales pa req equal parts 

parvus parv small 

pediluvium pdv a foot bath 

phiala phil a vial 

pilula pil a pill 

pulvis pul v a powder 

What beginning with Q ? 

quantum sufficiat.q. s as much as necessary 

quaqua hora q. h every hour 

What beginning with S ? 

saturatus sat saturated 

semissis ss a half 

semidrachma semidr a half drachm 

sesuncia sesunc a half ounce 

signa s. or sig .... a sign 

sine sine without 

solve, (verb) solv dissolve thou 

solutus sol a solution 


spiritus spir a spirit 

suppositoria suppos ... .a suppository 

syrupus syr a syrup 

What beginning with T '? 

tinctura tr a tincture 

tere simul ter sim rub together 

What beginning with U ? 

unguentum ungt an ointment. 

What beginning with V ?. 

vinum vin a wine 

vehiculum vehic a menstrum 

vitellus vit tne yolk of an egg 

vitello ovi solutus. v. o. s d "»egg e 

What Rule should guide a Physician in writing the abbre- 
viations of a formula ? 

He should never so carelessly write, or abbre- 
viate any part of a prescription, as to make it 
obscure or doubtful. 

Example — R. — Acid, hydro. 

Does this mean hydrochloric or hydrocyanic 
acid? It is exceedingly important to know 
which one is meant. Dr. Mann says justly: Pre- 
scriptions must be written as for the stupidest 
and most ignorant of apothecaries' clerks. 

What is the general Latin Rule for pronunciation ? 

In Latin, every word has as many syllables, as 
it has vowels or dipthongs, and must be pro- 
nounced accordingly. 

Example — Dilute, as a Latin word, has three 
syllables, and is pronounced — di-lu-te, and not 
di-lute, as the corresponding English word. 

Cochleare, is pronounced in Latin — coch-le- 
a-re, and not, coch-le-are, as in English. The 
Latin, divide, is pronounced, di-vi-de, and not 

86 student's manual of 

To this general rule, it may be added, that the 
English system, so called, of pronouncing the 
Latin, is the most rational for us as English 
speaking Americans, and, therefore, the sounds 
of the leading letters in Latin, are nearly the 
same as in our own language. Hence eh is 
always hard like k ; c and g before a, o and u, 
are alwaj^s hard and sounded like k. The same 
letters before e, i and y are soft; the c being 
sounded like s, and the g like j. C before the 
dipthongs se and ce, is likewise soft. 

Let the student convert the following unab- 
breviated formula taken from the Cyelopcedia. 
of Practice of Medicine, into the abbreviated 
form with the symbols andRoman characters: 

R. — Extracti taraxici, drachmas duas. 

Pottassse nitratis, drachmam semissim. 
Spiritus etheris nitrici, drachmam unam. 
Infusi cortisis auranti, uncias sex. 

Misce— S. Cochleare am plum bis terre die 

As everywhere in Europe, the directions here, 
to the patient are expressed in Latin. The 
translation is: A tablespoonful must be taken 
two « r three times a day. 

The student will, also, convert the following- 
abbreviated prescription from Stile's Therapeu- 
tics into unabbreviated Latin : 

R. — Magnena? sulpb, - - - fij 
Aq. mentha\ - - - i~x 

Acet. colchici, 

Syrupi simpl, - - - aa.l' r j 

Magnesese, ... g. CLX 

M. S.— Coch. parv. cap. 

The following prescription from Dr. Eberle, 
may be thus written out in both forms: 


B. — Carbonat. ammonia 1 , - - ?j 
Aq. fontame, - - - ?vj 

Mucil. g. arab, ... jss 
Syrup, zingerberis, - - sj 

M. S. — Tablespoonful three times daily. 

The same unabbreviated : 

Ijl . — Carbonatis ammonias, drachmam unam. 
Aqse fontanfe uncias sex. 
Mueilaginis gumi arabici, unciam sem- 

Syrupi zingerberis, unciam unam. 

Misce. Signa. cochleare amplum ter in die. 
Does not the Metrical System of the French wonderfully 

simplify all this ? 

It does; for it sweeps away at once all the 
long Latin numerals, all the old English sym- 
bols of weight, and the Roman characters. 
Besides, it relieves the prescription writer of 
all the Latin rules given above, except those 
relating to the genitive case, the sound of letters 
and pronunciation. 


Example — R.— Potas. accetat, - - - 5. 

Spts. sether nit, - - - 6.50 
Tr. scillse, ----- 4. 
Infus. scoparii, - - - 105. 
Why is this System called the French Metrical System ? 

Because near the beginning of the present 
century, it was first divised and adopted by the 
French Government, having a fixed value of 
length, called the meter, for its standard unit. 
Apart from its use in Medicine, what are some of its general 
advantages as a system of Weights and Measures? 

It is remarkably simple; twelve words will 
designate all of its various units of measure 
and weight ; and as in Federal money, which 

88 student's manual of . 

is also decimal, only a few of those twelve 
words are ever used in pract'ce. The entire 
system may be made gravimetric, as it is exclu- 
sively in medicine, that is, every object whether 
solid, or liquid, or gaseous, may be weighed, and 
never measured. A single denomination, the 
gram, serves all the purposes of the apbthecary, 
the decigram and milligram being discarded just 
as the dime and mill, are in writing and read- 
ing Federal money. 30.123 grams, is read 30 
grams, one hundred and twenty-three thou- 
sandths, or thirty grams twelve and three- 
tenths centigrams, just as it is read in Federal 
currency 30 dollars 12 3-10 cents. 

European pharmaceutists, where this system 
is well understood, and in constant use, never 
write, even the abbreviation for the gram, that 
quantity being the only one recognized, thus 
vastly lessening the chances of error in writing 
or compounding formulas. 

The milligram, a quantity so much more 
minute than the English grain, supplies a 
deficiency ever felt in our system; that is, the 
necessity of a unit of weight by which may be 
estimated the smallest quantity of matter, 
which a physician or druggist can be required 
to dispense. 

The multiplies and divisions of this svstem, 
are all decimal, and may, therefore, be multi- 
plied, divided, subtracted and added just as in 
simple numbers. Simply changing the place 
of the decimal point, is all that is necessary 
to reduce from one denomination to another. 
These are a few of the claims of the metrical 
system upon the good sense and enlightenment 
of the age in which we live. 


What is the Basis of the Metrical System ? 

The basis is the meter, a metallic rod, equal 
to 39.368 English inches, and divided into 
tenths, hundredths and thousandths. 
How are these decimal Divisions named ? 

The fractional divisions are designated by 
the word meter, with several Latin numeral 
prefixes. These prefixes are, milli, centi, deci, 
derived respectively from the Latin milli, cen- 
tum and decern. 
How are the decimal Multiples named ? 

These are named by prefixing the word meter 
with certain Greek numerals. They are deca, 
hecto, kilo, myria, formed respectively from the 
Greek meaning ten one hundred and one thou- 
sand times the unit. 
What are the several units of the system ? 

The unit of weight is the gram; of length, 
the meter; of surface, the are*; of capacity, 
the liter, f 

What are the, fractional denominations of length in full, 
and their abbreviations ? 

They are the millimeter, abbreviated mm. ; 
the centimeter, abbreviated cm ; and the deci- 
meter, abbreviated dm. 

What are the Multiplicative denominations and their abbre- 
viations ? 

The decameter, abbreviated Dm. ; the hecto- 
meter, abbreviated Hm. ; and the kilometer, 
abbreviated Km. The meter is abbreviated, m. 
What is the Table of Length ? 

10 mm. (0.001) make one centim 0.01 

10 cm make one dm 0.1 

10 dm make one m 1.00 

*Pronounoed like our English verb, are. 
t Pronounced lbeter. 

90 student's manual of 

10 m make one Dm 10.00 

10 Dm make one Hm 100.00 

10 Hm make one Km 1000.00 

How are the Denominations formed in each of the remain- 
ing measures ? 
By the same use of the Greek and Latin 

numeral prefixes with the respective units. 

What are the Denominations and Table of the Weight 

Unit ? 
10 milligrams (0 001.) ahbre. ms make one centig .......0.01 

10 c£ make one decig 0.01 

10 dg make one gram 1 00 

10 g make one Becg 10.00 

10 Dg make one Heetog.-.IOO.OO 

10 Hg make one Kilog.. ..1000.00 

What are the Denominations and Table of the Unit of 

Capacity ? 

10 milliliters (0.001) abbre. mm. make one centil 0.01 

10 el make one deciliter 0.01 

10 dl make one liter, 1 1.00 

10 1 make one decaliter Dl... 10.00 

10 Dl make one hrctoliler HI... 100.00 

10 HI make one kiloliter Kl. ... 1000.00 

What are the Denominations and Table of tlie Measure of 
Surface ? 

1 sqr. meter sqm. make one centare, ca. 

1(H) sqr. meters make one are. a. 
1000 sqr. meters make one hektare, ha. 

The Congress of the United States has legal- 
ized the following metrical equivalents : 

Meter= 39.37 inches. 

Liter == 1.06 Liquid quarts=0.908 dry quarts. 

Gram=15.482 grains Troy=0.035 ozs. Avoidu- 

Kilo =2.2 pounds Avoidupois. 

Are =3.95 square rods. 

Store or (cubic meter)=35.32 cubic feet. 


With these equivalents reduction from one 
system to the other are readily made. But for a 
proper comprehension of the metrical system, 
the American student must forget the old units 
and standards, and think, as it were, only in 
those of the new. To do this, he must procure, 
and study actual standards of the metrical 
measures, as he once studied the yard and foot 
units of the English system. 
What is the usual abbreviation of Kilogram ? 

It is kilo, a thousand grams, or the weight of 
one cuhic decimeter of water. 

What are the Denominations and Table of the Measure 'it 
Weigh - for heavy articles ? 

10 kilograms make one myriagram, rag. 
10.000 g. 

10 mg. make one quintal, q. 100.000 g. 

10 q. make one ton, t. 1.000000 g. 

The ton is equal to one cubic meter of dis- 
tilled water=1.000000 g. 

The kilo is equal to one cubic decimeter of 
distilled wat« r=1000 g. 

The myriagram is equal to ten cubic decime- 
ters of water=10.000 g. 

The gram is equal to one cubic centimeter of 
distilled water=to one milliliter. 

The liter is equal to one cubic decimeter of 
distilled water=to one kilo=1000 g. 

How does the Metrical System simplify the operation of 

finding the Specific Gravity? 

■In this system, as just stated, the weight of a 
liter of water at its maximum density, 39 F. is 
one kilogram ; hence the weight, in kilograms, 
of a liter of any liquid, or of a cubic decimeter 
of any solid, is the same as the specific gravity, 


What, again, is Specific Gravity ? 

It is the weight of any solid or liquid com- 
pared with the weight of an equal volume of 

A liter of pure water, weighs a kilogram, or 
1000 grams; but the liter is also a cubic deci- 
meter; therefore, when a liter of any liquid is 
measured, or a cubic decimeter of any solid is 
weighed, its specific gravity is obtained as well. 
Besides, it is often desirable to ascertain the 
weight of a large mass, which can be measured 
but not weighed ; or to find the bulk of some 
irregular solid, which can be weighed, but not 
measured. The specific gravity being obtained 
or given, such problems can be easily solved. 

Examples — A liter of alcohol weighs 835 grams ; what is 

its spe. gr. ? 

Apply the rule; divide the weight of the 
alcohol by that of a leter of water; 835 -f— 1000 
=.835— Answer. 

A centiliter of pure mercury weighs 140 grams, what is the 

spe gr. of pure mercury ? 

A centiliter is the hundredth of a liter; hence 
■a liter will weigh 100x140=14000 grams or 14 
kilograms — Answer. 

What is the spec. gr. of the water of the Dead Sea, if five 
liters of it weighed Gk. 2, that is six and two-tenth kilo- 
grams ? 
One liter will weigh the fifth of 6k.2=1.24 

grams — Answer. 

Three liters of whale oil weighs 2k. 760, what is its spe. gr.? 
One liter must weight the third of 2k. 769= 

0.923— Answer. 

A block of white pine is 60 cm. long, 15 cm. wide, and 10 
cm. thick, and weighs 3k.762, what is its spe. gr. ? 


The solid contents are 00x10x15=9000 cu. em.,, 
but a cu. cm. is one-tenth of a cu. dm. ; hence' 
9000 cu. cm. are equal to 900 cu. dm. and' 
3k.762-v900=one cu. dm. of the block, 0.418— 
What will four liters of honey weigh, if its spe. gr. be 


The four liters, will, of course, weigh four- 
times 1.456=5824 grains=5k. 824— Answer. 

What is the weight of 91.4 of ammonia water, its spe. a? 

being 0.875? 

The 91.4 will weigh, 9.4x.875=S.2250=3k.225 
— Answer. 
A walnut plank has a spe. gr. of 0.681, what will a plank 

weigh 3m. .5 long, 62 cm. wide, and 10 cm. thick? 

The solid contents are — 3.5x62x10=2170 cu. 
cm.; hence 2170=217 cu. dm.; but a cu. dm.= 
1000 grams; therefore, 0.681x217=147.777 grams. 
=147k.777 — Answer. 

The great bell in the French Cathedral at Montreal, weighs 
11263k. 6, if its spe. gr. is 8.7, how many cubic decime- 
ters does it contain ? 

It is plain that it will contain just so many 
as 8.7 is contained times in 11263. 6=1294.66-j- 
cu. dm — Answer. 

Can anything be plainer or simpler than all 
this? Keeping in view the definition of specific 
gravity, it may be, also, said that the same- 
number expresses in the metrical system, both 
sp. gr. and the weight of one cu. cm. of pure- 
water at the temperature of 39.2 F. This weight 
is one gram, so that the weight of one cu. cm. 
of any substance, at that temperature, ex- 
pressed in grams, is the same as its spe. gr. 
What important distinction is it necessary to observe here- 
again ? 


The difference between spe. gr. and density. 
Spe. gr. is mere ratio; it conveys no other mean- 
ing than the relative, abstract number which 
•expresses it. Water being one, iron weighs 7.8; 
seven and eight-tenths of what? Density, on 
the contrary expresses, water or any other sub- 
stance being one, an absolute division or mul- 
tiple of the fixed value of the standard unit. 

"What then is the admirable point here, in the French 

It is that they have taken the same unit, one 
■cubic centimeter of pure water, to express both 
the unit of volume and the unit of weight. 
"The same number, therefore, which expresses 
spe. gr. expresses density as well, it is this 
principle that makes it possible and easy as 
above, to obtain- spe. gr. from weight, and 
weight from spe. gr. and volume from both, as 
in the following example : 

An ingot of copper of spe. gr. 87.9, weighs .'Usg. 963 bow 

many cu. cm does it contain? 

Since the spe. gr. of the copper is its weight 
compared with a cu. cm. of water, it must con- 
tain just so many cu. cm. as 8.79 is contained 
times in 34S.g. 963=39.7 cu. cm— Answer. 

No such convenient arrangement is found in 
the English system of weights and measures. 
It is true that a cubic inch of pure water is 
taken as the standard or unit of weight, but 
the same unit is not likewise the standard of 

Is not this principle, also, one of the most notable features 
of the New Chemistry ? 

This characteristic of the New Chemistry, 
chiefly distinguishes it from the old. The same 


principle has been introduced there, except that 
hydrogen gas is the standard unit instead of 
water or air. 

It is still convenient, however, in Chemistry, 
to refer occasionally to air as the unit in spe. 
gr. but hydrogen gas, at the temperature of 
0°C. and the pressure of 700 mm. is the Chem- 
istry standard for spe. gr. and density, the 
latter, as explained above, being an absolute 
value from the fixed value of the standard unit, 
while the former is mere ratio. 
What is the name of the Stan lard Volume of Hydrogen in 

Chemistry ? 

It is called the Ckith, a criterion or standard 
from the Greek Kritces a judge. 
What quantity of Hydrogen constitntes this un't? 

One liter which weighs, 0.0896 grams. This 
is the Crith. 

What are the Density and Spe. Gr. of Hydrogen in Chem- 
istry ? 

Its density is 1 ; its spe. gr. referred lo air is. 
0.0693. 1 as a number, expressing ratio, may be 
also, regarded as its spe. gr. in the chemical 
sense, for it may he taken abstractly, and not 
as the crith. But it is agreed to restrict the 
word density to mean the actual weight of a 
gas referred to the hydrogen atom as a standard. 
What is this Standard called and why? 

It is called the miceocrith, or the little 
criterion; and is so named, because it is just 
one-half the crith, which represents, always a 
molecule or two atoms of hydrogen. 
What is the Molecular Weight of any Gas ? 

It is the weight of one liter of that gas, com- 
pared with the hydrogen liter or crith, and 



represents, therefore, the weight of two atoms 
of it. s 

What then is the relation of Molecular Weight to Density ?' 

Since molecular weight represents the weight 
of two volumes, and density one, the density of 
any perfect gas is the half of its molecular 
weight. This is the same as to say, that the 
weight of one liter of the gas, divided by the 
crith, or 0.0896 grams gives its density. 

The first method is by calculation, the second 
by experiment. 

Example— The molecular weight of water is 
18; this number divided by 2, gives 9 as the 
density of steam. Again, let a liter of steam or 
water gas, be weighed; it is 8047 grams; 
divide this number by the crith, or 0896, and 
the result, as in the first case, is 9, rearly. These 
processes inform us, that steam is nine times as 
heavy as hydrogen ; and this, in the case of any 
gas, is its density. 
What is the converse of this Principle ? 

Knowing density, molecular weight is ob- 
tained by simply doubling it. 

What is the importance of density in an Analytical point of 
view ? 

It is necessary in any case, in order to ascer- 
tain the true molecular weight. 

In these investigations, what does mere Analysis of any 

homogeneous substance give only? 

It gives certainly only the ratio of its consti- 
tuents, and not their absolute weight of volume. 
Hence analysis, ma}' or may not yield the true 
density of the substance. 
If a liter of the substance, in the form of gas, could be 

obtained and weighed, would that clear away ail doubt? 


Yes; were a liter of its vapor once accurately 
weighed, then all uncertainty in regard to its 
density, as has been seen, and all that depends 
upon density — molecular weight, molecular 
volume, specific gravity and atomic weight, 
would be at an end. 

Example — Water may be taken again; the 
analysis of water shows that in 100 parts of it, 
there are 1111 of hydrogen to 88 89 parts of 
oxygen,* which numbers reduced to their lowest 
terms give the ratio 1 to 8. Is 8 the density, or 
actual weight of an atom of oxygen referred to 
hydrogen? The Old Chemistry said it was, 
because its atomic weights were mere ratios, 
and of density it knew nothing. But 2 and 16, 
3 and 24, 4 and 32, and 5 and 40, all have pre- 
cisely the same ratio— 1 to 8. Which of these 
several sums is the true density of water ? 
Analysis, obviously, makes no certain response. 

The question was decided above, by experi- 
ment, when the weight of a liter of steam was 
divided by the crith. 

Knowing the Crith, as the weight of a cu. cm. of pure 

water is known in the French metrical system, may not, 

as seen tlvre, spe. gr. density, molecular weight, and 

molecular volume, be readily ascertained ? 

The weightof aliterof anysubstance in vapor^ 

referred to hydrogen, is its density; the double 

of this number is the molecular weight. The 

same number which expresses density, gives 

the specific gravity, referred to hydrogen, also 

the molecular volume, since it is referred to a 

molecule of hydrogen, and besides, as will be 

seen in its proper place, the atomic weight of 

the same substance. 

*18:16::100:=88.89. 18:2::100:=11.11. 


Example — A liter of oxygen gas weighs l(i 
times the crith ; 16 is, therefore, its density; 
and 2 its molecular volume ; twice 16 or 32 its 
molecular weight; 1G is also, its spe. gr. re- 
ferred to hydrogen and its atomic weight. 
Knowing the Specific Gravity of Hydrogen referred to air, 

may not the spe. gr. of any other substance be easily 

obtained ? 

The spe. gr. of hydrogen referred to air is, 
0.0693; it is plain, therefore, that if this num- 
ber be multiplied by the density of any other 
substance, the product must be the spe. gr. 

Example — The density of oxygen is 16, what 
is its spe. gr. ? 0693x16=1.01 — Answer. 
What is the Specific gr, of Chlorine ? 

The density of chlorine is 35.5, hence 0.693 
x35. 5=2. 46— Answer. 
What is the spe. gr. of Mercury V 

The density of mercury is 200; 200x.0693= 

Such are a few of the admirable simplifica- 
tions in the principles and methods of the New 

Metrical Pharmaceutical Weights Compared 
with the English. 

It is best, of course, for younger pupils to 
study and master the Metrical System without 
any reference to the units, and standards of the 
one, yet in use in this country; but as this is 
impossible for the greater number who may 
study these pages, it is expedient to append, 
here a comparitive view of the values of the 
two systems. 


In the Metrical System, we have no other 
quantity to consider, than the gram and its 
fractional units. 

1* grain=.06 grams. 1 ounce=31 grams. 

1 scruple=l 30 grams. 15grains=l gram. 

1 drachm=4 grams. 

What is the Rule for converting any quantity in English 
weight, into Metrical grams ? 

Toe previous table suggests it. Reduce the 
quantity to grains, and divide by 15, the num- 
ber of grains in a gram. 

What is the Rule for a similar reduction of the higher de- 
nominations ? ' 
Reduce the quantity to drachms, and multi- 
ply by 4 or reduce it to ounces and multiply 
by 31. One gram of water is equal to 16 2 
minims, and the same rules are applicable 
nearly in the conversion of fluid measures into 
What is the Table of Fluid equivalents? 

1 M or minim=.06 grams. 
1 f 3=3.75 grams. 
1 f 5=30. 00 grams. 
Having the above tables and rules, may not any common 
formula be readily converted into gram weights ? 

Let the student change the formulas on pages 
86 and 87 into metric weights. 

R- — Magneste sulph, - - 5"ij=62 grams. 

Aq menthte, - - f 3x=300 grams. 

Acet. colehici, - 

Syrupi simpl, - - aaf 5.j=30 grms. 

Magnesise, - - - gr CLX =10.6 grams. 
R. — Carbonat. ammoniac, - - - 3j= 

Aq. fontse, 5vi= 

Mucilag g. arab, ... - ^ss= 

Svrnp. zinaerberis, - - - - ^j= 

* quantities are a little less than the real values. 



What is the Rule for converting any number of grains, 
whether fractional or entire, into equivalent expressions 
in grams ? 

We have seen that 1 grain is equal to .065 
grams; hence multiply this number by the 
number expressing the grains, and the result 
will be the grams. 

Example— 49 grains are equivalent to what 
number of grams? .065x40=2.60 — Answer. 

1-64 of a grain is equivalent to what in 
grams? .065xl-64=.001 — Answer. 

By this rule, a pupil can in an hour, construct 
and paste up in liis room a table that will save 
him much after trouble. When he reaches 20 
grains, let him mark it also, 13, 60 grains, 13 
and 120 grains, 23. 

In order to change liquids into equivalent 
gram weights, some regard must be had for the 
difference of spe. gr. But this can be readily 
cleared up, and made easy in practice. 
What Liquids of the Pharmacopoeia are lighter than water? 

They are tinctures, spirits, comp. spirits of 
ether, sweet spirits of nitre, and fixed and vola- 
tile oils. 
What Liquids are heavier ? 

These are syrup, glycerine, a few fluid ex- 
tracts and chloroform. Among the fluid ex- 
tracts, Dr. Squibb includs squills, liquorice, wild 
cherry, aconite and cubebs. 
What Liquids are nearly or quite the same in spe. gr. with 

water ? 

They are waters or liquids generally, decoc- 
tions, infusions, most fluid extracts and tinc- 
tures in dilute alcohol. 

What table expresses these differences of spe. gr. for the 
minim of grams ? 





Spe. Gr. of 



Lighter than 



Heavier than 


1 ilin. 




By wruit Rule then can a minim of any liquid be reduced to 
equivalent weight in grams ? 

If the given liquid be of the same spe. gr. 
with water, multiply the number expressing it 
by. 06; if lighter than water by .055, and if 
heavier, by .08. 

What is the weight in grams of 8 minims of 
a liquid lighter than water? 8x.055=.45 — 

Let the student construct for his use, a con- 
venient table from these data. At 60 minims, 
he will mark lf3, and at 250, fjss. It will be 
observed that the metric system in its applica- 
tion to Pharmacy is purely gravimetric; that is 
it weighs every thing and measures nothing. 
In every country where it has been adopted, it 
is customary to weigh not only solids but 
liquids as well. The adoption of the gravima- 
tric, in place of the present mixed volumetric 
and gravimetric methods, should go hand in 
hand with the adoption of the metric system.* 

It is quite probable that the next United 
States Congress will adopt and legalize the 
metric system, hence the greater necessity for 
its careful study. The pupil would do well to 
provide himself with the following apparatus: 
Several straight rods, 20, 30 or 50 centimeters 
long; a few pieces of tape, 2 or 3 meters long; 
a cup and a basin ; a little drj 7 sand, and several 
stones of a kilo, and half, fifth and tenth kilo 

''Louisville Medical News. 


weight. A small balance would, also, be quite 
useful.* With these, he could soon familiarize 
himself with the concrete values of the units 
of the system ; for, after all, this is the chief 
difficulty in the way of its general adoption. 

When we speak, for example, of a meter, we 
have, first, the novelty of the name to confuse 
us, and yet more, in the fact, that no conception 
enters the mind from experience, as to what a 
meter's length really is. The same remark is 
true of all the units of the. svstem; but with 
the use of the apparatus, described, clear, and 
correct notions of these standards are soon 

The names, which make up the simple nom- 
enclature of our system of Federal money, and 
for which the- country is under last-ng obliga- 
tions to the practical mind of Thomas Jefferson, 
of Virginia, were, once, no less strange to us, 
than are, now, those of the French system of 
weights. Mill, cent and dime, have a kindred 
form and origin, with milli, centi and deci; 
but joined, as they are, to the admirable deci- 
mal system whose values they bear, the gjod 
sense of the people soon approved them, and 
now what citizen would desire to exchange it 
for the clumsy system which our fathers brought 
with them from the mother countrv ?f 

"Bulletin of the American Metric Bureau. 

tThe subject of Metrical Weights and Measures, as a univer- 
sal system, has been treated in a masterly manner, in a letter 
addressed to Mr. A. H. Stevens, by .Mi-. Samuel Barnett, of 
Washington, Ga., a gentleman, whose aouteness of intellect 
and admirable, moral and social worth, merit the highest 
honors of his State. 

cssjecc rnYgics. 103 



What is a general Definition of Light ? 

It is that physical agent by which we are 
enabled to see. 
What is Optics? 

It is that branch of Physics which treats of 
the properties and laws of light. 
How did the Ancients regard Light? 

They believed that light was, in some way, 
produced in the eye, and its emission, thence, 
caused vision. 
What is the modern Belief? 

That light exists independent of the eye, and 
that something coming into the eye from with- 
out excites the sense of vision. 
AVhat does the Pentateuch say of Light ? 

" And the earth was without form aifd void, 
and darkness was upon the face of the deep, 
and the Spirit of God moved upon the face of 
the waters, and God said let there be light, and 
there was light, and God saw the light that it 
was good, and God divided the light from the 

So that whatever light is, whether a form of 
motion or a material substance, it had its ex- 
istence before any eye was formed. 
What are the Sources of Light ? 

The sun, stars, chemical action, electricity 
and phosphorescence. All bodies are either 
luminous or non-luminous. 


What are Luminous bodies ? 

They are bodies in which light is generated, 
and from which it is emitted independently of 
all others. 

Example— The sun and a candle. 
What are Non-Luminous Bodies ? 

These are bodies, which shine only, as they 
are shone upon, as the moon. They may be 
called illuminated bodies. 
What is a Transparent Body ? 

It is one, which like glass, does not arrest the 
passage of light. 
What is an Opakque Body ? 

It is a body whose molecules arrest the rays 
of light in their passage, as the metals. 
What is the Law of the distribution of Light ? 

From whatever source it eminates, it moves 
in straight lines. The lines along which it 
moves are rays of light, and these rays form a 
cone, whose base is the pupil of the eye, and 
whose *pex is on the object seen. 
This is the Divergence of Light ; what is its Law ? 

The surface over which, in any case the base 
of the cone is diffused, increases as the square of 
the distance increases. That is, if a lamp illu- 
minates from a window four square feet of a 
wall in front of it, at twice the same distance, 
it will illuminate four times the space or six- 
teen square feet. 
What is the Law of the Intensity of Light? 

The intensity of light, as it goes out from a 
luminous point, diminishes as the square of the 
distance increases. That is, at a distance of 
two feet, the intensity will be only one-quarter 
of what it is at one foot. 

UJiUMU'ii-i-mmin. 105 

What is the Velocity of Light ? 

The velocity of light, as determined by Rce- 
mer, from • the eclipses of Jupiter's moon, is 
182,560 mi es per second. M. Fizeau, by ex- 
periments over terrestrial distances, found it 
to be 194,677 miles per second. Bradley, in 
1723, in Kew Gardens, England, discovered the 
aberration of light, and thence the velocity of 
light, to be 161,515 miles per second. 
What is the Aberration of Light? 

" If we move quickly through a rain shower, 
which falls vertically downward, the drops will 
no longer seem to fa 1 vertically, but will appear 
to meet us. A similar deflection of the rays of 
light from the stars by the motion of the earth 
in its orbit, is called the aberration of light." 
How is the Velocity of Light calculated from this ? 

It is the solution of a simple prob'em in plain 
Trigonometry. Knowing the speed, at which 
we move through a shower of vertical rain 
drops, and knowing the angle, at which they 
appear to descend, we can readily calculate the 
velocity of the falling drops. Hence knowing 
the velocity of the earth in its orbit, and the 
angle, at which the rays of stellar light appear 
to bend towards us by that motion, the velocity 
of light is easily calculated.*. 
What is Photometry ? t 

It is the measurement of light. 
How may the difference in Intensity of two or more d fferrnt 

Lights be ascertained ? 

This process is based upon the law of inten- 
sity already given, and the fact that the more 

*Prof. Tyndall's Notes on Light. 

yFrom rims, Light and Metron, measure— Greek. 


intense a light is, the darker will be its shadow. 
Let the shadow of a walking cane be cast 
upon a white screen by means of a flame 
placed behind it; and let another flame be 
placed beside the first; a second shadow will 
appear close to the first. Now if the two flames 
have equal intensity, these shadows will be 
equally dark ; if not, let the more intense flame 
be moved back till the shadows do exactly cor- 
respond in depth. If the two distances be now 
measured, and their numbers squared, we will 
have a numerical expression of the relative in- 
tensity of the two Haines. Suppose the num- 
bers to be 2 and 4; then the relative intensity 
is as 4 to 16. 

What is Catoptrics? 

Catoptrics* is that branch of Optics, which 
treats of reflected light. 
What is the Reflection of Light ? 

When a ray of light strikes any surface, 
which causes it to rebound in another direction, 
it is reflected. If it be not reflected, it is either 
in part absorbed or transmitted by the surface. 
If the surface is polished, it will be regularly 
reflected; if not, the light will be scattered. 

What is the' Law of Reflection ? 

The angle of reflection is always equal to the 
angle of incidence. Up->n this law, hang all 
the phenomena of optics. 
What is a Mirror ? 

It is any polished surface which powerfully 
reflects light. There are three kinds, plane, 
concave and convex mirrors. 

*From the Greek, kata down u'pon, and optomai to look. 

CHEMlUO-±"llXaitiS. 10T 

When does a Mirror* reflect most light ? 

When the angle of incidence is most oblique. 
A basin of water and a candle will illustrate 
this; as the same with a plumetline suspended 
from a cross piece graduated in inches will de- 
monstrate the law of reflection. The scale runs 
from zero, the point of suspension, in opposite 
What is an Image in Optics ? 

It is a figure of any object formed by reflected 
rays proceeding from every point of it. 
In what direction is an Image always seen ? 

An image is seen in the direction of the rays 
which proceed from it. Oblique rays show an 
image on one side of the mirror, and as far 
behind as the object is in front of it. Perpen- 
dicular rays are reflected back along their own 
course, and show an image directly behind the 

Ave there not two Primary Reflections from every mirror?' 
An oblique reflection shows a series of images 
over-lapping each other, and if it is veryoblque 
and the glass thick, these images may be quite 
separated. The first image is from the reflec- 
tion of the light from the anterior surface of 
the mirror; the second, and the brighter one, is 
from the reflecting surface of the amalgam at 
its back. 

The other images of the series are formed by 
the reverberation of the light from surface 
to surface of the mirror. The larger the inci- 
dences, the brighter the reflections from the 
amalgam surface, and the less those from the 

*A looking glass and a candle will afford the pupil many- 
interesting experiments in this connection. 

108 student's manual ok 

In what respect will an linage alwa} - s differ from its object? 

The image must present a lateral inversion 
of the light. Hence any piece of composition 
in type may be read in a mirror as the same 
matter on the prin'ed page. 

What interesting Phenomena seen in p'ane Mirrors arc all 
the c mtequence of the law of reflection ? 

First — A plane mirror, one-half the height 
of an object, gives a full height image of the 

Second— A plane mirror moving parallel with 
itself, will cause an image to move with twice 
its velocity. 

Third — A plane mirror made to revolve, the 
angle described by the image, will be twice that 
described by the mirror. 

Fourth— If a plain mirror be inclined at an 
angle of forty-five degrees, the image of an 
object erect, appears horizontal, while tbe image 
of one horizontal appears erect. 

Fifth — If an object be placed between two 
mirrors forming an angle with each other, a 
number of images will appear; and the number 
Avill increase as the value of the angle dimin- 
ishes. This is the principle of the kaleidoscope. 
To find the number of images, divide 360, the 
number of degrees in a circle, by the value of 
the given angle. When the angle is zero, then 
the n nmber of images is infinite. It is usually 
-60° the sixth of the circle. 

Doe^ the same Law of Reflection apply to Concave and 

vConvex Mirrors ? 

They have the same law ; and by them rays 
from all terrestrial objects may be made par- 
allel or convergent; they are naturally diver- 



Let MN be a portion of the circumference 
ence of a circle, having its centre at 0. Let the 
line ax, passing through lhe centre, cut the arc 
M N, at o. in two equal parts Now imagine the 
curve MN to be revolved around the line ax as 
an axis. It would describe the segment of a 
hollow sphere, whose inner surface, when pol- 
ished, is a concave mirror. All parallel rays, 
such as come from an infinite distance or from 
the sun, as dM, are reflected from the mirror 
along the line M F, and made to converge at the 
point F, half way between the mirror and the 
centre O. F is, therefore, called the principal 
focus of such a mirror, or the focus of parallel 

Let a candle be placed in that focus, then re- 
ciprocally, the rays will le reflected parallel 
along M d, and go out without forming an image, 
for they converge in no focus. Let the candle be 
placed at the centre O, then the rays will be re- 
flected back along the same line M 0, for the 
reason, again, that by the law, the angle of re- 
flection is equal to that of incidence. 

110 student's manual ok 

If the candle be placed at the point x, beyond 
the centre 0, the reflection will be along the 
line Mi, to x, a point between the. centre and 
F, where the image will appear. If reversed, 
as before, the image will appear at x. Now let 
the candle be placed at the point G, between the 
mirror and the principal focus, and the rays of re- 
flection will go out, as along the lines Mb and Nc, 
divergent, and will form no image before the 
mirror, but a virtual image behind it, at the 
point E. The image, here, is said to be virtual, 
because a.t the point E the rays appear to con- 
verge; and it has been remarked, that objects 
are always seen in the direction of the rays 
which reach the eye. 

When an image is formed behind a concave 
mirror, it is always erect and magnified in pro- 
portion as the object approaches the focus F. 
When an object is further from a concave 
mirror than its true focus F, the image will be 
inverted, and smaller than the object, if the 
image fall between F and 0, greater if beyond 0. 


What is Refraction of Light? 

When light passes through one medium into 
another, as from air into water, instead of pro- 
ceeding in a straight line, it is bent out of its 
■course. This is refraction. 
What is the law of Refraction ? 

When the rays pass perpendicularly through 
one medium into another, they move in a 
straight line; when obliquely through a rarer 
into a denser, the}'' are bent generally towards a 


perpendicular to the surface ; but when they 
pass through a denser into a rarer medium, 
they are generally bent away from the same 

This important optical law is thus expressed 
mathematically : The sine of the angle of inci- 
dence, divided by the sine of the angle of refraction, 
is a constant quantity. In this form the law is 
Why is it modified above bj' the word generally? 

This is best explained by an example. It is a 
notable fact that refraction by spirits of turpen- 
tine is greater than that by water, though the 
density of turpentine to that of water is 874 to 
1000. A ray, however, passing obliquely from 
the spirit into water, is bent from the perpen- 
dicular; while a ray passing from water into 
turpentine, is bent towards the perpendicular. 
Hence the reason of the use of the modifying 
word generally. 

What are the Indices of refraction for water and other 
familiar substances ? 

The index of refraction for water, is 1.336 ; 
of vinegar, 1.334; of brandy, 1 360; alcohol 1.372; 
of turpentine, 1.605; of bisulphide of carbon, 
1.678, and of the diamond, 2.439.* 
What is the principle of reversibility in Refraction ? 

It is that result of the law, which restores the 
ray, after a series of refractions, to its original 
direction in its first medium. This is seen, 
every day, in the natural appearance of objects 
through window panes. 

What familiar effect has refraction upon water, or any trans- 
parent plate ? 

112 student's manual of 

It makes them to appear shallower or thinner 
than they really are. 

What is the relation of Refraction to Reflection ? 

They constantly go together; when one ceases 
the other ceases also. 
What is the Law of this relation ? 

The higher the refractive index of any sub- 
stance is, the greater is its power of reflection. 
This is the cause of the unrivaled splendors of 
the diamond. 
What chemical relation has Refraction ? 

The power of refraction, is the only property 
of matter, except weight, which is unaltered by 
chemical combination. The physical law is: 
the greater the density, generally, the larger the 
refractive index. 

What is the comparative value of the refractive index of a 


It is very small, and in consequence gases 
both reflect and refract light feebly. The re- 
fraction of the atmosphere has, however, to be 
taken into account by astronomers and engi- 
What is a Lens? 

It is any refracting substance, bounded by 
curved surfaces. 
How are Lenses classified ? 

They are studied in two classes : 

First — Those which render parallel rays con- 

Second — Those which render the same rays 
divergent. There are three kinds in each class. 

What are these ? 



First— Double convex. 

Second — Plano-convex. 

Third — Concavo-convex (Meniscus). 

First — Double concave. 

Second — Plano-concave. 

Third— Concavo-concave. 
What is the principal axis of a Lens ? 

It is a straight line drawn through the centre 
of the lens and perpendicular to its two convex 
What is the principal Focus of a Lens ? 

All rays falling upon the lens, parallel to the 
axis, are made to intersect at a point on the 
axis behind the lens. This point is the princi- 
pal focus, and is the*focus of parallel rays. 

How does the convex lens, as in the case of the concave 
mirror, become a burning glass ? 

It does so in virtue of its power to converge 
parallel rays to a focus, concentrating, thereby, 
on one point a high degree of temperature. A 
lens of this sort is capable of instantly fusing 
the metals and liquefying quartz and flint rock. 
Do Convex Lenses form Images? 

They form images in their foci in the same 
way as do concave mirrors. 
Why are these Images always inverted ? 

Because the rays of light in passing from the 
several points of the object, cross each other 
before they meet in the focus. 
Why do Convex Lenses magnify ? 

Because in virtue of their power to make rays 
converge, these after refraction, seem to enter 

114 student's manual of 

the eye from points more distant from each 
other than they really are. 

Why can not a Spherical L< ns bring all the rays that fall 
upon it, to the same focus ? 

Because the rays which fall upon or near its 
circumference, are more refracted than those 
which pass through its central portions, and 
are, therefore, brought to an earlier intersection. 
This difference of focal distance between the 
central rays and those of circumference, is 

What is an Aplanatic Lens? 

It is a lens composed of two or more lenses of 
different curvatures, neutralizing aberation.* 
What is the Human Eye? 

It Is a compound lens, in three parts; the 
aqueous humor, the crystaline lens, and the 


Why does the Pupil cf the Eye always appear black? 

For two reasons : 

First — Because of the internal black coating 
of its posterior wall. 

Second — Chiefly, because we are notable ordi- 
narily, to see the spot of illumination when it is 
illuminated, since, as has been constantly ex- 
hibited in all reflection and refraction, the 
principle of reversibility comes into play. The 
rays on returning from the bright spot, must by 
this principle, intersect to form their focus or 
image in the source of illumination; hence the 
impossibility of seeing the illuminated spot, 
unless the eye of the observer, be placed between 
the pupil and the source of illumination; but 
this cuts off the rays of light. There is a device 

•Aplanatic from the Greek a, privative, and pianarthac,U> 

. s: ::r . :^,v •,■■;:- sics. 115 

by which this difficulty can be obviated. Let a 
small hole be pierced through a mirror; the eye 
can now be strongly illuminated, and, at the 
same time, observed through the orifice from 
the back of the mirror. This is the Ophthal- 
moscope, one of the most important contribu- 
tions to Surgery of the age. Under this instru- 
ment the interior of the eye glows like a coal 
of fire. 

Why does tbe eyes of Albinos and White Rabbits appear 
red ? 

Because the black pigment is wanting and the 
pupils are seen by light, which traverses the 
sclerotica. Cut off this light and their pupils 
are black. 
What aimirable Instrument was modeled from the eye ? 

The eye is a Camera Obscura,* with its re- 
fracting lenses. The ground glass of the Camera 
on which its images are pictured, is its retina. 

Since imaies on the reiina are inverted, why are objects 
always seen erect ? 

Because the eye is so constructed, that every 
point of an image painted upon the retina, is 
seen in a direction perpendicular to the 


hence, it is absolutely necessary to have an 
inverted picture of an object on the retina, in 
order to see it erect. 
What conditions are necessary for perfect %'ision ? 

That the object should be placed before the 
•eye, and that the rays of light reflected from it, 
should form a perfectly defined image upon the 

*This beautiful piece of mechiuism should be carefully 
studied by the pupil. 

116 student's maxcal of 

Why are some persons Far-Sighted ? 

Because in many old people, and some youth T 
the axis of vision is too short; that is, the dis- 
tance from the centre of the cornea to the 
retina. In this case the image is formed behind 
the retina instead of upon it. 
Why are some persons Near-Sighted ? 

Because in many young people, and some old, 
this same axual distance is too long. In this 
case, the image is formed before the retina, 
instead of upon it. 

In near-sight, the defect is remedied by hold- 
ing the object very close to the eye, so as to 
increase the divergence of the rays; hence the 
popular name. 

In far-sight, it is remedied, habitually, by 
holding the object some distance from the eye, 
so as to lessen the divergence. 

What is the artificial remedy for Near-sight? 

It is remedied by placing before the eyes, a 
concave glass or lens. This augments the di- 
vergence to the necessary degree. 
What for Far-sight? 

By placing before the eyes, a convex lens, 
which sufficiently lessens the divergence. 
Why do Drunkards and Cross-eyed people see double ? 

Because they are unable to fix the optical axes 
upon the same point or object, so as to convey 
but a single impression to the brain. 
What is the Angle.of vision ? 

It is the angle at the eye subtended by any 
object of vision. The larger this angle, the 
greater the size of the object. Distance, also, 
affects this angle. 


Is the Eye a perfect optical instrument? 

It is not ; it is frequently defective from spher- 
ical aberration. A confused scattered light al- 
ways exaggerates the images of luminous objects 
vipon the retina. It is this, that causes the cres- 
cent moon to appear larger than the sphere to 
which it belongs. 
Can the Eye see objects in itself? 

It can ; the well known muscse volitantes, are 
images of this kind. They are caused by opaque 
bodies flecking the humors of the organ ; and 
these would be a constant source of annoyance, 
if less light reached the retina through the 
pupil. The flood of light obliterates their 
What is a Microscope ? 

It is an instrument, which so magnifies minute 
objects, as to make them distinctly visible to 
the eye. It effects this by enlarging, as has 
been exhibited, the angle of vision under which 
the object is viewed. 
How many kinds of Microscopes are in use? 

There are two; the simple and compound. 
In the first, the object is viewed directly, either 
by a simple or compound lens; in the second, a 
magnified image of the object is first formed, 
and this again, is viewed with magnifying 
How is the Instrument usually constructed ? 

The simple microscope is usually a tube con- 
taining a single double convex lens. The com- 
pound microscope contains, in addition, another 
double convex lens, which magnifies the image 
formed by the first lens These are called, re- 
spectively, the object and eye glasses. 

118 student's manual OF 

An illuminating mirror, is also a common 
adjunct of the microscope. 
What is a Stereoscope?* 

It is an optical instrument by means of which, 
a picture on a flat surface, appears to stand forth 
as a solid. 
Wlat is the principal of its action ? 

It was first ascertained that the images of an 
object within the two eyes, are different from 
each other. We can see only one point of an 
object d stinctly, at a time; now if these two 
different sides of the object are so laid before 
the view as to be taken in at once, the effect is 
the visual impression of a solid. 
What is a Prism ? 

Any body of glass having two plane surfaces 
not parallel, is a prism. 
What is the action of the Prism ? 

On looking through a pri-m, all objects ap- 
pear to be removed out of their true places. 
Why is this? it is because its planes are not 
parallel. It was seen in another place, that 
when we view objects through a pane of window- 
glass, they all appear natural. Why is that? 
It is because the sides of the pane are parallel, 
and in this case the reversibility of refraction fol- 
lows; that is, the rays recover, on emergence, 
the precise direction they left on their first re- 
fraction from the air. 

The ray in the prism is permanently refracted. 

How did the Prism, in the hands of Newton become an 
exceedingly valuable instrument? 
By means of it he revealed the mysteries of 

* From the Greek, stereos solid and metron, measure. 


solar ligh*-, and opened the way for the discov- 
ery, in our time, of Spectrum Analysis. 
What is Dispersion ? 

When solar light is serjt through a prism, its 
constituent rays are drawn asunder. This sep- 
aration of the elements of light, is called diS' 
What is the cause of Dispersion ? 

Luminous bodies generate in ether waves of 
various length; some are shorter than others. 
In passing through the prism, the short waves 
are more retarded than the longer ones and 
hence are more refracted. The result is separa- 
tion or dispersion. 
What is a Spectrum ? 

It is the luminous image of white light formed 
by its decomposition in the prism. 
What is the Soltrr Spectrum? 

When the white light thus decomposed, comes 
from the sun, the image is the solar spectrum. 
Of what does the Polar Spectrum consist? 

It con-ists of a series of vivid colors, which, 
when again blended, produce the original white 
What are those colors, and their order in the Spectrum ? 

Beginning with ihe one least refracted, they 
are red, orange, yellow, green, blue, indigo, 
and violet. 
What determines the color of these elements of white light? 

It is determined in each case, solely by the 
wave length. The gradation diminishes from 
red to violet. 
What are the extremes of this scale of wave lengths ? 

The length of a wave of red light, is nearly 

120 stidknt's maxl'ai. of 

jainrr of an inch, of a wave of violet about rriws 

of an inch. 

How many waves of Red Light enter the eye in a second ? 

As many as the product of 39000 by 186398, 
the velocity of light. 
How many of Violet ? « 

The product of 186398* by 57500. 

How is Color related to Sound ? 

It is to light, what pitch is to sound. 
Is the Spectrum confined to its visible limits ? 

It extends considerably beyond in both direc- 
tions. Above the violet is a great body of rays, 
having no heat or light force, but powerfully 
endowed for chemical action; and beyond the 
visible red, are rays without light force, but 
of high heating power. 

What gives Color to objects around us ? 

All bodies absorb light, but this capacity is 
selective ; some ra3'S of the spectrum are absorbed 
while others are rejected. This gives variety of 
Where does the color of a body reside, on its surface, or in 

its interior ? 

It reflects white light, always from its surface. 
The color comes from the extinction of certain 
rays within the body. 
What is Chromatic Aberration ? 

Like " Spherical Abberration,'' it is due to 
irregular refraction. A spherical lens is inca- 
pable of bringing its different colored elements 
to a common focus 

'Since giving the velocity of light on page 1(>">, Mr. A. A. 
Nicholson, of the United States Naval Academy, has made -a 
new determination of the velocity of light, i>\ means of a lens 
of 150 feet focal distance The result is li;s,:!i«i miles. 


Has this been corrected by Opticians ? 

Chromatic aberration was believed by Newton, 
to be an insuperable difficulty in practical 
optics. The problem was to produce refraction 
without dispersion, and therefore, decomposi- 
tion of light. He thought that dispersion must 
ever be exactly proportional to refraction. This 
is now known to be untrue; and even lenses are 
constructed, which refract and are achromatic* 
How is this affected ? 

By so combining a convex crown glass lens 
with a concave flint glass lens, as to neutralize 
on refraction, the dispersive effect of the convex 
lens. The residual refraction is achromatic. 
Was this discovery of great importance in the construction 

of the Telescope and Microscope ? 

Previous to this, it was impossible to produce 
either of these instruments in their present 
comparative perfection. 
What are Subjective Colors ? 

They are colors, which have their origin in 
the peculiar condition of the eye, and not in the 
external conditions which produce the sensation 
of color. 
What is Daltonism? 

It is the color b'indness, which is now known 
to afflict so many people, disqualifying them 
for positions that require quick discrim nation 
between colors, as engine drivers. John Dalton 
was unable to distinguish a ripe, red cherry 
from a green leaf. 
What is Spectrum Analysis ? 

The colors produced by the prism are not only 

*From the Greek, a negative and chroma color. 



pure and elementary, but it has been found that 
the incandescent vapor of every substance, re- 
veals through that medium a color or combina- 
tion of colors ; e uUar to Uaelf. Spectrum analy- 
sis, therefore, is the analytical examination of 
light from any source by means of a prism, or 
.system of prisms, arranged in an instrument 
called the spectroscope. 
How many kinds of Spec'rosco;-es are there? 

There are two; the compound and the direct- 
vision Spectroscope. 
What is the Simple or Direct-vision Spectres' ope ? 

In this in- 
strument, the 
slit, admitting 
the light, the 
prism and lens 
a n d telescope 
viewing the 
spectrum, are 
all arranged 
Fig. 15. in the same 
straight tube. This is sometimes made so mi- 
nute that it can be carried in the pocket. 
What is the Compound Spectroscope? 

This splendid triumph of mechanical and 
scientific skill is composed mainly of four parts: 
1st. A tube containing a lens, and the knife- 
edged slit for admitting the light. The lens 
refracts the light parallel upoif the prism. 

2d. A telescope by which the spectrum is 

3d. A tube containing a lens for refracting the 
image of a measuring scale near to, and parallel 


with the spectrum, in order to estimate the 
width of the lines and their intervals. 

4th. The prism or prisms, in the centre of the 
arrangement, by which the light is refracted, 
and sometimes re-refracted. See Fig. 15. 
What are the Spec'ral Lines ?* 

Newton, in his experiments on light, used a- 
round hole for its admission, which was sufficient 
for his great discovery of the decomposition of 
light. In 1802 Wollaston substituted a slit for 
the round orifice, and now a new era dawns upon 
the science of Optics, for this slit revealed the 
fact that the solar spectrum is not pure, but is- 
crossed in many points by dark lines. Here the 
matter rested for twelve years longer and was 
Who next took up the investigation ? 

In 1814,aGermanoptician, named Fraunhofer, 
made experiments on light, using the English- 
man's slit to form his spectrum, and added a 
telescope for the purpose of viewing it. At that 
moment, new and curious facts in the spectrum 
dawned upon the vision of Fraunhofer. He 
counted 590 of these dark lines between the red 
and the violet, and found that they varied in 
width and were unequally distributed in groups 
along the spectrum. What do these lines 
mean? That was the problem. Fraunhofer 
rightly conjectured what they are, but died be- 
fore its verification. 
What was Fraunhofer's Conjrcture ? 

He believed that the cause of the dark spec- 

* It is a curious fact that for 127 years, the progress of knowl- 
edge, as respects the capabilities of the prism in the analysis 
of light, was held in check, for the simple reason of the differ- 
ence between a sjiall kousd hole axd a slit. 

124 student's manual of 

tral lines exists in the sun. What had become 
of the missing rays? 

What wa^ the next important step towards the solution of 
the problem ? 

In 1842, Dr. Draper added to the spectroscope 
used by Fraunhofer, a photographic plate of 
very sensitive surface, by which he nearly 
doubled the number of lines seen by the 
German, and experimented for the first time 
■on the spectra of incandescent, familiar solids 
and gases. He discovered that the spectra of 
incandescent solids are without lines of any 
kind, while those of gaseous bodies, were known 
to be striped and broken with bright lines, and 
«ach with its own peculiar line or lines. The 
vapor of potassium gave three; two red, at one 
•extremity of the spectrum, and one purple at 
the other. Sodium gave bright yellow lines, 
while iron exhibited several hundred such 
lines peculiar to itself. Oxygen, hydrogen, and 
nitrogen had, also a spectrum distinctive for 
each. What do these bright lines mean? Are 
they in any way connected with the dark lines 
of Fraunhofer? Thus the problem seemed 
more complicated, yet really near its solution. 
Who next took it up and unraveled the mvstery ? 

This was done by Kirchhoff (Keerkhoff) in 
1859. He was engaged in mapping the bright 
lines of some of the metals; and in order to 
■effect this more conveniently, he had placed 
Fraunhofer's spectrum over another that its 
dark lines might guide him. And now a reve- 
lation came to Kirchhoff, which solved the 
problem of the dark lines, and gave to Chem- 
istry the most refined method of analysis yet 


There stood sixty of the characteristic bright 
lines of iron, exactly coincident with as many 
of the dark, in position, width and grouping. 
What does this mean? Philosophy could give 
but one answer. The equation of chances 
showed that there were a pentillion of chances to 
one, that it was not accidental, but a result in 
the sphere of cause and effect. What is that 
cause ? The old German's conjecture had been, 
realized, and there was but one step more. 

How did Kirchhoff demonstrate the causal relation of the 
bright and dark lines ? 

He and others showed by experiment that 
these lines are reversible; that the bright 
lines of any gaseous substance, such as sodium, 
when it passes through its own vapor, before 
being refracted, are replaced by coincident 
dark lines in their spectra. That the rays from 
incandescent thallium vapor, are intercepted 
by thallium vapor, those from lithium vapor, 
by lithium vapor, and so of other metals. 

On ■what principle or Law, then, did Kirchhoff base his 
explanation of the Lines of Fraunhofer ? 

Upon this law. That every substance is especially 
opaque to such rays as it can itself emit when made 

The same law may be thus stated in the lan- 
guage of the "undulatory theory;" waves of 
ether are absorbed with special energy, or their 
motion is taken up with special ease, by atoms 
whose periods of vibration synchronize with . 
the periods of the waves. 

How is this principle illustrated in Acoustics? 

When a musical string is tuned to a certain 
note, if that note be sounded, the string will 

126 si 

soundin unison. That is, it readily absorbs 
what it was toned to emit, or it takes up with 
ease the motion with which its own molecular 
motions synchronize. 
How is it illustrated by Radiant Heat? 

It is a well known principle that a body ra- 
diates heat in the proportion that it absorbs 
heat. A good radhtor is a good absorber. 
What is the special application of the principle? 

For example incandescent sodium vapor emits 
a bright yellow band; therefore, sodium vapor 
readily absorbs yellow, by the principle. In- 
candescent, potassium vapor emits red and pur- 
ple, hence potassium vapor easily absorbs those 
What is, now, the necessary inference, which elevates us. at 

once, into Solar Physics? 

It follows irresistably, that the dark lines of 
Fraunhofer, represent, each line or each system 
of lines, that substance in the sun's photosphere, 
whose incandescent vapor there has stripped it, 
by absorption, of its characteristic color before 
its prismatic refraction here. 

" Let the light from the sun, and the light 
from incandescent sodium vapor, pass side by 
side through the same slit, and be decomposed 
by the same prism. The solar light will pro- 
duce its spectrum, and the sodium light its yel- 
low band. This yellow band will coincide ex- 
actly in position with a characteristic dark band 
of the soar spectrum, which Fraunhofer marked 
with the let'.er D. 

Were the solar nucleus absent, and did the 
vaporous photosphere alone emit light, the dark 
line D, would be a bright one. Its character 

.n^uv-.u 127 

and position prove it to be the light emitted by 
sodium. This metal, therefore, is contained in 
the sun."* 

What other Metals were discovered by the' same process, in 
the Sun's Atmosphere ? 

The metals cnlcium, barium, magnesium, iron, 
chromium, nickel, copper, zinc, strontium, cad- 
mium, cobalt, rubidium, manganese and alumi- 
num. Hydrogen is also there, but no ozone, 
nitrogen nor carbon. f 

What effect had the explanation of Fraunhofir's lines upon 
our knowledge of the Sun ? 

It introduced a new theory of its constitution, 
that it consists o F a solid or molten central nu- 
cleus intensely incandescent, and inveloped in 
a gaseous photosphere, whose vapors absorb the 
rays, which they themselves emit. Hence the 
lines of Fraunhofer. 

Who soon after extended the Spectrum Analysis to the light 
of the stars, planets and nebulae? 

This was done by Alex. Huggins, and now we 
have not only Solar but Planetary, Stella and 
Nebular Physics. 
What does it teach of the Planets ? 

It teaches us that light there, is the same as 
the light of the sun; that it loses nothing by 
its passage through space, has its dark heat and 
chemical rays as well; that the moon has no 
atmosphere and that the constituents of the 
planets Lre quite similar to each other and to 
those of the sun. 

* Tyndall on Light. 

t How much more convincing is KirchhofF.s reasoning, 
"when this coincidence of bands was seen in the case of the 
«bove metals having many bright bands ; as nickle having 33 ; 
•calcium 75 ; manganese 57 and iron at least 470. 

128 student's manual of 

What does it tell of the Fixed Stars ? 

That light there is still the same in its con- 
stitution and phenomena ; that the unity of the 
universe is unbroken, for in the star Aldebaran, 
are found hydrogen, sodium, bismuth, antimony, 
mercury, iron, calcium and magnesium. Hy- 
drogen has been discovered in so many hundred 
of the fixed stars that it may be regarded as the 
universal element. 
What does it reveal of the constitution of the Nebulas ? 

It reveals the fact that many of the nebulae 
are gaseous, as they were long supposed to be, 
since the spectra of many of them, give only 
the bright bands of known elements. Hydrogen 
and nitrogen are there. 
What facts indicate the delicacy of the Spectrum Analysis ? 

It will detect the presence of t? to hux,vo * of a 
grain of sodium, euiruouo of a grain of lithium, 
and the .001 part of a grain of the coloring 
matter in a blood stain. 
What new Elements has it revealed ? 

It has added to Physics four new elements, 
viz., caesium, rubidium, thallium and indium. 
What are the practical Uses of this Analysis ? 

It is invaluable to the Bessemer steel-making 
process, for the spectroscope indicates the exact 
moment in the spectrum, when carbon disap- 
pears from the converter. It promises to be of 
precious value in many chemico-legal cases, in- 
dicating the .001 of a grain of blood in a stain 
made more than a half century before. It will 
detect the most delicate physiological changes 
in the animal system, and discriminate readily 


between wines of a new or old vintage These 
are only a few of the achievements of this won- 
derful process, and it is yet but in the infancy 
of its applications and developement. 

Under what condition, alone, will substances yield their 
characteristic bands in the spectroscope ? 

In the condition, only, of an incandescent vapor. 
This vapor does not form a continuous spectrum, 
that is, the colors do not gradually fade into each 
other, but by an increased power of different 
refrangibilities, are grouped into distinct, col- 
ored bands. These spectra, then, consist of a 
series of colored lines, siugle or grouped, with 
intervals of darkness. 


What is meant by Interference of Light ? 

When light from different sources passes 
through the same tract of ether, the different 
waves set in motion, must affect each other. 
This is interference of light, when the effect of 
one is modified by that of the other. 
In the motion of waves, do particles of matter progress, or 

mere motion ? 

As in the case of a bird upon the water, the- 
waves progress, but not the bird ; he only osci- 
lates up and down. 
What is the extent of this Interference and what is it like? 

If the crest of one wave correspond with that 
of another, the effect is increased; but if crest 
correspond with sinus or depression, light is- 
annihilated and darkness results. It is like 
sound and heat motion: add sound to sound 
silence is often the result; add heat to> hea.t r 
and the effect may be cold. 

230 student's manual of 


What is Double Refraction ? 

It is the result which follows the splitting of 
a ray of light into two, the one rapid and the 
other slow, as it passes through certain sub- 
stances, f 
"What is the cause of Double Refraction ? 

It is the consequence of a peculiar arrange- 
ment of the molecules in certain bodies, which 
eauses them to possess different degrees of 


spar, or crystalized lime carbonate; rock-crystal 
and tourmaline. 

As respect Refraction, how do all crystals divide them- 
selves ? 

Into two classes : 

First— Single refracting crystals, as rock-salt, 
alum and fluorspar. 

Second — Double refracting crystals, as Iceland 
spar, rock-crystal and tourmaline, which have 
but one optical axis, and arragonite, felspar, crys- 
talized sugar, mica, heavy spar, sulphate of lime 
and topaz, which have two axes. 

Polarization of Light.— Polarization by Reflection. 

What is meant by the Polarization of Light? 

It is that peculir condition, which a ray of 
light acquires, after being reflected at a certain 
angle, from familiar polished surfaces, such as 
i-ater, glass, etc. 

Why is it termed a Po'ar condition ? 

Because Newton, who first saw it by refraction 
m Iceland spar, said that the beam of light had 


acquired, by its passage, siden; and compared 
this two-sidedness of the beam to the two- 
endedness of a magnet. Hence the polarity of 


What is Polarization by Refraction ? 

It is the same peculiar condition, which a 
beam of light acquires, on passing obliquely 
through crystals and plates of glass. 
How is the Polarization of Light accounted for? 

An ordinary beam of light is the vibration 
of the ether in all directions perpendicular to the 
line of it* motion. But, after certain reflections 
or refractions, these vibrations take place in a 
single p'ain only, either vertical or horizontal ; 
hence the altered reflections or refraction of the 
changed beam by the molecules. 
Is Polarization confined to crystalized bodies ? 

All substances, whether organic or inorganic, 
whose atomic arrangement is such, as to impart 
to the ether vibrating in them, different elasti- 
cies in different directions, are capable of polari- 
zing light. 

Does not this principle supply an important auxiliary to 
chemical analysis? 

It is used, in this way, in certain practical 
analyses of such bodies as cane and grape sugar, 
tartaric acid, oil of turpentine, albumen and 
uncrystallizable sugar. 
How is this application explained ? 

It depends upon a discovery by Biot, to the 
effect that certain organic substances of a liquid 
or semi-liquid consistence, exhibit a property 

132 student's manual of 

of polarity, called circular polarization. When 
placed between two prisms of peculiar structure, 
the rays are stopped or transmitted according 
as one of the prisms is related through a certain 
angle either to the right or to the left; and the 
extent of this rotation is in proportion to the 
concentration of the liquid and the thickness 
of the mass of it. 
How are these indications designated ? 

One is termed right-handed polarization, and the 
other left handed "polarization. 
What is the Polariseope ? 

It is an instrument by which light is polarized 
and examined. 
How is it constructed ? 

A refracting polariseope is made of prisms of 
Iceland spar, known as Nicol's prisms. This is 
the best instrument. 

A reflecting polariseope is made of two plates 
of glass, one of which polarizes the light and 
the other examines it. 
What are the Chemical Raj-s of Light? 

Like heat rays, the chemical rays of light are 
invisible, and being more refrangible than any 
luminous rays, are situated in the solar spectrum 
above the violet rays. 
AVhy are these rays called the Chemical rays of Light? 

Because it can be shown, that they act chem- 
ically upon certain bodies, producing decompo- 
sition and combination. 
Are these rays, of all in the solar spectrum, the most active 

in promoting vegetable growth ? 

It appears that they are not, for it has been 
proved that it is in the yellow ray, where there 
is no *atinic or chemical force, that the decom- 
position of carbonic dioxide is most active. 


How do Heat-rays, Light-rays and Chemical-rays differ from 
each other? 

They differ as yellow differs from green, that 
is by wave length and intensity of vibration. 
They are all affected alike by interference and 
In what four forms does Light manifest its effects upon 

matter ? 

1st. It alters elementary matter and gives it 
allotropic forms. 

2d. It powerfully induces chemical combina- 

3d. It produces mechanical effects. 

4th. It effects chemical decomposition and 

What Art has its ba?is in chemical decomposition and com- 
bination by Light ? 

The valuable art of Photography. 
What is Photography ? t 

It is the art of painting by means of Light. 
How does Light effect this ? 

It effects it chiefly through certain compounds 
of silver, which are exceedingly sensitive to the 
influence of light, becoming decomposed by it 
and changed in co'or. 
What is Phosphorescence ? 

It is luminous motion of the molecules of 
certain substances, caused by the etherial undu- 
lations in the absence of the sun. This being 
most familiar in phosphorous, is called phospho- 
What is Fluorescence ? 

It is that kind of phosphorescence, in which 

* Youmaii. 

t From the Greek, photos, light, and grapho to write or 


the chemical rays of the solar spectrum, become 
luminous in such substances as fluor spar and 
solution of sulphate of quinine. 

Meteorology— Methods of Observation— Instruments. 

What is Meteorology ? 

It is that branch of Physics, which considers 

all the natural phenomena, whether terrestrial 

or atmospheric, that depend upon the action 

of heat, light, electricity and magnetism. 

What two important branches are embraced in this defini- 
tion ? 
Climatology and a large part of Physical 


What is the object of Meteorology ? 

Its objects is to determine the various and 

constantly changing influences of heat, light, 

electricity and magnetism in the atmosphere 

and on land and sea. 

Is Medicine interested in the study of Meteorology ? 

Obviously it presents a field abounding with 

great and valuable results, both present and 

future for Medicine and Hygiene. 


What is a convenient form of a Weekly Meteorlogical 

Report ? 

The following table is sufficiently practical, 
and quite simple. 


Condensed from observations taken at the 
office of the State Board of Health, State 
Capitol, Atlanta, Georgia, for the week ending 
. 1880. 

<_'1IKA1H.:U-I'M 1 




* a i o •* 

Monday I 7 82 68 

Tuesday ' 8 85 65| 

Wednesday 9 85 i 

Thursday 110,82 

Friday '11 89 

Saturday 12 90 i 

Sunday '13 92 ' 


■2* Mi 


76.481 28.878 

.41! 4.1 


♦Corrected for temperature. 

Range for the week: Temperature, 12 ; barometer, .516 in. J 
ozone, 3' 2 . 

Fogs on the night of the 21st. Ozone deficient most of the 

This table condensed with the addition of two 
or three heads of observation, constitutes a 
tabular report for the month. It may contain 
some twelve primary heads or columns. 

First — Days of the month. 

Second— Thermometer in open air — mean of 
weekly readings. 

Third — Psychromcter — mean of wet and dry 

Fourth — Pressure of vapor in inches taken 
from elastic tension table according to barometer. 

Fifth — Relative Humidity or per cent of satu- 

Sixth — Absolute Humidity or grains of vapor 
in cubic foot of air. 

Seventh— Readings of Barometer and Ther- 
mometer attached reduced to freezing point. 

Eighth — Clouds. 

Ninth— Winds. 

Tenth — Ozone. 


Eleventh — Registering Thermometers — Max- 
imum and Minimum. 

Twelfth— Rain and Snow — Beginning of rain 
•and snow — Ending of same'— Inches of Ram and 
.Melted Snow— Depth of Snow. 

The above heads can be easily put in tabular 
form by the student. 
'What is the simplest method of ascertaining the amount of 

precipi a'ion of atmospheric moisture? 

The simplest form of a rain-guage is a cylin- 
drical vessel, it may be of tin, five or six inches 
deep, having vertical sides. This is exposed 
freely and just so near to the surface* of the 
ground, that no water may run into it, in each 
rain storm, and the water caught, afterwards 
measured in cubic inches. 
What is the construction of the Raiu-Guage or Udometer? 

It may consist of a cubical box of tin or zinc, 
■exactly ten inches in each side, open iibove. 
At an inch below its edge, it receives a funnel, 
sloping to a small hole in the centre. To the 
top of one of the edges, communicating with 
the interior, is soldered a short pipe, fitted with 
a stopple. This completes the instrument, 
which should be well painted. 
' This gauge is freely exposed, as beforehand 
the water, naught afterwards, measured in a 
cylindrical glass vessel, graduated to cubic inches 
and the tenths of cubic inches. 

Hence, one inch in depth, of rain in the gauge, 
equal to 100 cubic inches, will fill 100 inches of 
the graduated vessel ; and one inch of the same 
vessel will indicate 1.100 of a cubic inch of rain. 
The 1-10 of the graduated vessel will, of course, 
indicate the 1-1000 of a cubic inch. 

* The quantity of water caughl depends, in pail, upon the 
height ai wtiicii the gauge is placed. 


Does the amount of Humidity m the atmosphere, depend 
upon the quantity precipitated in rain? 

Not at all; it may be less where there is a large 
rain-fall than in other places, where there is 
little rain. 
Upon what does atmospheric humidity depend ? 

In any locality, it depends upon the presence 
of large areas of undrained, saturated lands, 
wide-spread swamps, lagoons, marshes and dense 
forests. The more a country is cleared and 
drained, the dryer and healthier it becomes. 
Is it imp< rt:m\ in a sanitary po'nt of view, that the amount 
of humidify in the atmosphere should be ascertained ? 

This is a question of the first importance to 
the people of any locality or country — far more 
important than an inquiry as to the presence of 
carbonic dioxide or carbonic oxide. A good hy- 
grometer should be in as frequent use in a dwel- 
ling, as the ever present thermometer. 
How is the amount of water in any fill of snow asceitained? 

A column of snow is caught in a cylinder, as 
so much rain, and after being melted, measured 
as before, as so much rain. Ten inches of snow, 
usually make one of rain. 
When are observations made for the average i.f Cloudiness? 

At 7 a.m., 2 p.m. and 9 p.m., daily. The av- 
erage per cent, of c'oudiness is given for each 
How is this ascertained? 

For a per cent, estimate, of course, 100 must 
represent entire cloudiness; 50, that half the 
sky is covered with cl< uds ; 0, that the sky is 
perfectly clear, and the intermediate numbers 
the intermediate per cent, of cloudiness. 
When are observations made for Rain and Snow? 

138 student's manual of 

The same hours which are used for observa- 
tions on cloudiness, and a like average found 
for days and months. 
When are observations made for Atmospheric Pressure? 

At the same hours, and the average readings 
of the barometer are taken as before. 
What remarkable fact, vouched for by the Smithsonian In- 
stitute, indicates the y;reat importance of Barometric ob- 
servations in Health Reports? 

In extreme cases the change of atmospheric 
pressure amounts to nearly one pound per sq. 
inch of surface. If then 2,000 sq. inches repre- 
sent the body of a man of average size, there 
may be in an hour, a difference of atmospheric 
pressure upon it, of some 2,000 lbs. According 
to Dalton, the superficies of the lungs amount 
to 201600 sq. inches; so that upon body and 
lungs, together, this difference of pressure may 
reach 203600 sq. inches or more than 101 tons. 

Can these changes take place, without corres- 
ponding, great and serious changes, in the phy- 
siological conditions of all who may be exposed 
to them ? If the barometer be rising, this must 
greatly increase the labor of the heart, aud ten- 
sion of the large arteries; if falling, it must 
produce serious disturbance in the nervous and 
vascular systems. 
When are observations made for Ozone? 

At the same hours, 7 a.m., 2 p.m. and 9 p.m. 
An average is then taken according to a stale 
of ten degrees of coloration. 
By what means arc the observations on Ozone taken ? 

By means of Schonbein's tes f -paper, a strip of 
Avhich is exposed at the hours designated. Alter 
exposure, it is compared wi h the given scale of 
ten degrees of coloration. See Ozone Scale. 

. wm acs. 139 

How are Schoubien's Test-Papers prepared? 

Schonbein's test consists of s'rips of paper 
moistened with a dilute solution of potassium 
iodide and starch. 
How is this last explained ? 

Ozone decomposes the iodide, setting the 
iodine free, which combining with the starch, 
strikes a deep blue color. Having, now, a stan- 
dard of ten degrees of different shades of this 
characteristic blue, it is easy, by comparison, to 
find an average of the daily, monthly, and an- 
nual observations.* 

Temperature.— Placing of Thermometer. 

How should the open-air Thermometer be placed ? 

1st. It should be so placed as not to be affected 
by the direct rays of the sun or any heated body. 

2d. It should be suspended on the North side 
of some thin wall, from a bracket some six 
inches from the wall. 

3d. It should not be exposed to the open face 
of the sky. This causes it to give too low a 

The mean temperature is obtained by taking 
the sum of the three observations and dividing it 
bg three. 

Barometer.— Atmospheric Pressure. 

How should the Barometer be placed, and observed ? 

1st. It should be suspended in-doors, in a room 
of uniform temperature. 

2d. It should have a good light, but no expo- 
sure to the direct rays of the sun. 

"The test-papers must be kept in'closed bottles in a dark 


140 student's manual of 

3d. Its position should be exactly vertical. 
To observe it — 

1st. Note the temperature of the attached 
thermometer; the heat of the bodv may affect 

2d. Adjust the cistern, by causing the mer- 
cury just to touch the ivory point. 

3d. Gently tap the case to loosen the adhesion 
of the mercury to the tube. 

4th. Enter in their proper columns, both the 
reading of the barometer and that of the attached 

Humidity of the Atmosphere.— Hygrometers. 

w r ] at is absolute Humidity? 

It is the number of grains or grams of vapor 
contained in a definite por.ion, as a cubic foot, 
of vapor. 
What is relative Humidity ? 

It is the ra io of the quantity of vapor con- 
tained in the air, to the quantity it could con- 
tain, at the observed temperature, if fully sat- 
How is absolute Humidity ascertained? 

It is con veniently ascertained from tables, and 
on page 27 is given Daniell's Table, abridged 
from his Meteorlogical Essays, which shows ab- 
solute humidity for temperature, Fa. in English 
measure. Here, for the sake of increased accu- 
racy, and variety, we add a more elaborate one, 
calculated in metric vnlues. 

Weight of one Cubic Centimeter of Atmospheric Air, in 
Grams, al Different Temperatures for every 5 degrees from 

to 50° C. at 760 mm, ami tin- every '.' degrees from '.V>° to 
122 V. 





32° F. 






























j 40 


' 001128 










How may this table be practically applied ? 

Example — What is the absolute weight of 1 
cub. cm. of air at 40°C ? this being the temper- 
ature of observation ? 

Weight of 1 cc.m. at 40° = 0-001128— Ans. 
What is the weight of 1 cc.m. of air for 42° ? 

Weight of 1 cc.m at 45° =0.001111 

Differ, between 40° and 45°= 17 

Add 3-5 of 17 to 0.001111 = 0.001111 + 10 = 
0.001120— Ans. for 42°. 

By the column of differences, we are enabled 
to calculate the intermediate values. If the 
questions had been asked in Farenheit, the in- 
terpolation of difference would have been 9ths 
instead of 5ths. 

Record the results of these three daily baro- 
metric observations in their proper columns, 
and at the end of each month take their sum 
and average. 
How is Relative Humidity ascertained ? 

Relative humidity is expressed in hundreths 
or per cents., full saturation being equal to 100. 

142 student's manual of 

It is easily calculated from the indications of 
■dew-point instruments. And as in absolute 
weight, tables have been prepared which greatly 
facilitate the work. 

These observations merit special attention. 
The Monthly Register of Meteorlogical Obser- 
vations of the State Board of Health of Michi- 
gan, justly remarks ; ■' The amount of moisture 
in the air is a matter of great importance, both 
in a meteorlogical and in a sanitary point of 
What is the object of Dew point Instruments ? 

" The object of every dew point instrument," 
says Dr. Guyot : "Is to ascertain, by causing a 
part of the apparatus to cool, the temperature, 
at which the vapor contained in the air begins 
to condense, in the shape of light dew on the 
cooled portion of the instrument."* 
If the temperature of the Dew point be known, may not all 
the hygrometrical conditions of the air be easily deduced 
from it ? 

They may. The Absolute Humidity, or the 
total amount of vapor in the atmosphere, is ex- 
pressed by the number, in the tables of elastic 
forces of vapor, already given, due to that tem- 

The Relative Humidity, or the degree of 
moisture, being the ratio of the quantity of 
vapor actually contained in the air, to the 
quantity it could contain, if fully saturated, is 
expressed by the proportion. 

"Dr. Guyot prepared, before the recent war, for the Smith- 
sonian Institute, a collection of Tallies, Meteorlogical and 
Physical, which culled from the ablest scientific sources in this 
country and Europe, embodies all thai is most reliable and 
practical on the subjects presented. These tables, methods and 
Formula are the basis of observations In all the signal stations 
of the Union. 


Maximum Force of Vapor: Force of Vapor 
at Dew-point : : 1 : Relative Humidity. 

Calling the Force of Vapor at the Tempera- 
ture of the Dew-point, f. 

Force of Vapor at the Temperature of the 
Air, F ; the proportion becomes, F : f : : 1 : hence 
Relative Humidity = p- 

This formula gives the rule: Divide the force of 
vapor, as given in the Table of Elastic Forces, cor- 
responding to the temperature of the dew point, by the 
maximum of the force of vapor, due, in the same 
table, to the temperature of the air at the time of the 

But since relative humidity is the object 
of inquiry, F* must be always greater than /. 
Hence relative humidity is expressed by a frac- 
tion, termed the fraction of saturation. Perfect 
saturation being represented by 100, in order to 
obtain this fraction in hundredths, the formula 
must be written: Relative Humidity= ~ X J^ 
How is this Formula or Rule practically applied ? 

Example — Temperature of Air or t = 62°F. 

Temperature of Dew-rt>int or t =53°F. 

Number in Table of Elastic Force, correspond- 
ing to 62°F. = 580. (See page 27.) 

Number corresponding in same table to 
53° ==420. 

We have interpolated for difference, at sight, 
20, in each number, this being sufficiently ac- 

By the formula then; 420x100—^580 = 
72 4. Ans. 

All that is necessary, therefore, for these ob. 

*F is always necessarily greater than f when the air is not 

114 student's manual of 

servations, is to find the temperature of the clew- 
point from Daniell's hygrometer or the wet and 
dry thermometers, also the temperature of the 
air from the dry bulb thermometer, and having 
obtained the ; r respective tensions from the table 
of Elastic Forces, substitute those numbers in 
their proper places in the given formula.* 

What is the most convenient instrument to be used in this 
observation ? 

The humidity of the air is easiest measured 
by means of the wet bulb and dry bulb thermome- 
ters; and these being quite sensitive, and com- 
bined in one instrument, is called the Psychro- 
meter, from the Greek psukrvs, cold, and metron, 
measure. The tables calculated for its readings 
are known as Psych rometrical Tables. 
How should this instrument be placed for observation? 

The Psychrometer should be so placed, as to 
be freely exposed to the air, observing all the 
precautions given in connection with the Ther- 
mometer in the open air. The covering of the 
wet bulb, should be renewed often enough to 
secure cleanliness. A syringe will generally 
purify it without its reftoval. Rain water, only, 
should be used with this instrument. The cov- 
ering should be wet, at least, fifteen minutes 
before each observation, unless it is covered with 
ice, for evaporation goes on from the solid as 
well as from the liquid state. If the tempera- 
ture be at or below the freezing point, the ther- 
mometer will mark 32° till all the water is frozenf 

* Table VIII, page 75 of Guyot's Smithsonian Report, saves 
all trouble of calculation in these observations j but this table 
and others in the same work, are too extensive for our space. 

t Sec direetions in Monthly Register of State Board of 
Health, of Michigan. The annual reports of this Hoard reflect 
distinguished honor upon their government and people. When 
will the Legislature of Georgia, vindicate by a similar institu- 
tion, the wisdom and intelligence of her people ? 



Why is it important to make observations on Ozone ? 

"Observations on ozone are desired, as one 
element of climate, but especially to ascertain 
its relations to health and disease. Observers 
are requested to notice and record any apparent 
connection which the abundance or deficiency 
of ozone may have with the prevalence or 
absence of any given diseases, or its modifica- 
tion of their types."* 
What casual Phenomena is it important to note ? 

Thunder Storms,) Time of occurrence and direction 

> / of motion, width, and direction 

iornadoeS, f of path, effects produced, whether 

t» ,» i \ attended by electricity or hail and 

Earthquakes. ; size of hail. 

Meteors and Shooting Stars, their direction 
and time of occurrence 

Aurora Borealis, its time of occurrence and 

Earthquakes, time of occurrence, direction of 
impulse, number of shocks and effects. 

Note all unusual phenomena. 

•Michigan Monthly Register of Health Reports. 




Atom 8 

Air Pump 43 

Amorphism 49 

Atmosphere 33, 139, 140 

Avogadro's Law 34 

Barometer 38, 139 

Boyle's Law 33 

Biology 8 

Bunsen's Burner 15 

Chemistry, definition of 7 

Cell 60 

Clinical Thermometer 13 

Condensation 16 

Cryophorus 18 

Cupping Appa 46 

Crystallization 49 

Chromic acid batte 62 

Cryth 95 

Catoptrics 106 

Chromatic Abera 120 

Color 119 

Daltonism 121 

Density 32 

Dew 23 

Density of Gases 20 

Diffusion of Gases 46 

Dispersion 119 

Defervescence .• 15 

Distillation 17 

Daniell's Battery 61 

Element 10 

Ebullition 16 

Electricity 54 

Electrical Battery 57 

Electro-Physiology 67 

Electro-Surgery 69 

Electro-Diagnosis 68 

Electro-Therapeutics 71 

Expansion 11, 16 

Expansion of (iases 19 

Exhausting Syringe 45 

Eye 114 

Faradaism 76 

Faradization 69 

Far-Sight 116 

Fluorescence 163 

Galvanism 57 

Galvcnometer 67 

Galvanization 69 

Galvano-Cautery 70 


dove's Battery 61 

Goueometer 62 

Heat 11 

Heat-Unit 20 

Hygrometer 24. 27, 140 

Hydromter ISO, 32 

Humidity 142 

Joule's Law 20 

Latent Heat 18 

Osmoze 47 

Ozone 138, 14.5 

Physics 7 

Pneumatics 33 

Pipette 76 

Poles 59 

Polarization 130 

Phosphorescence 133 

Prescriptions 76 

Prism 118 

Psycrometcr 144 

Refraction 110, 111 

Refraction, Double 130 

Reduction of Gases 34 

RuhmcorfPsCoil 66 

Science 7 

Specific Gravity 21,29, 31 

Smee's Battery 61 

Spectrum 119 

Spectrum Analysis 121 

Stereoscope 118 

Sublimation 52 

Syphon 37 

Specific Heat 11 

Thermometer 12, 139 

Torricelli 37 

Vaporization 11, 16 

Vapor, Tension of 24 

Vacuum 36 

Weights 28, 73, 98 


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